Support uppercase characters in slugs (gosimple#34)

Fix gosimple#29

README.md

@@ -31,6 +31,10 @@ func main() {
 
 	deText := slug.MakeLang("Diese & Dass", "de")
 	fmt.Println(deText) // Will print: "diese-und-dass"
+
+	slug.Lowercase = false // keep uppercase characters
+	deUppercaseText := slug.MakeLang("Diese & Dass", "de")
+    fmt.Println(deUppercaseText) // Will print: "Diese-und-Dass"
 
 	slug.CustomSub = map[string]string{
 		"water": "sand",

languages_substitution.go

@@ -30,11 +30,11 @@ var deSub = map[rune]string{
 	'&': "und",
 	'@': "an",
 	'ä': "ae",
-	'Ä': "ae",
+	'Ä': "Ae",
 	'ö': "oe",
-	'Ö': "oe",
+	'Ö': "Oe",
 	'ü': "ue",
-	'Ü': "ue",
+	'Ü': "Ue",
 }
 
 var enSub = map[rune]string{
@@ -83,15 +83,15 @@ var trSub = map[rune]string{
 	'&': "ve",
 	'@': "et",
 	'ş': "s",
-	'Ş': "s",
+	'Ş': "S",
 	'ü': "u",
-	'Ü': "u",
+	'Ü': "U",
 	'ö': "o",
-	'Ö': "o",
-	'İ': "i",
+	'Ö': "O",
+	'İ': "I",
 	'ı': "i",
 	'ğ': "g",
-	'Ğ': "g",
+	'Ğ': "G",
 	'ç': "c",
-	'Ç': "c",
+	'Ç': "C",
 }

slug.go

@@ -28,7 +28,11 @@ var (
 	// after MaxLength.
 	MaxLength int
 
-	regexpNonAuthorizedChars = regexp.MustCompile("[^a-z0-9-_]")
+	// Lowercase defines if the resulting slug is transformed to lowercase.
+	// Default is true.
+	Lowercase = true
+
+	regexpNonAuthorizedChars = regexp.MustCompile("[^a-zA-Z0-9-_]")
 	regexpMultipleDashes     = regexp.MustCompile("-+")
 )
 
@@ -76,7 +80,9 @@ func MakeLang(s string, lang string) (slug string) {
 	// Process all non ASCII symbols
 	slug = unidecode.Unidecode(slug)
 
-	slug = strings.ToLower(slug)
+	if Lowercase {
+		slug = strings.ToLower(slug)
+	}
 
 	// Process all remaining symbols
 	slug = regexpNonAuthorizedChars.ReplaceAllString(slug, "-")

slug_test.go

@@ -66,38 +66,46 @@ func TestSlugMakeLang(t *testing.T) {
 		lang string
 		in   string
 		want string
+		lowercase bool
 	}{
-		{"de", "Wir mögen Bücher & Käse", "wir-moegen-buecher-und-kaese"},
-		{"de", "Äpfel Über Österreich", "aepfel-ueber-oesterreich"},
-		{"en", "äÄäöÖöüÜü", "aaaooouuu"},
-		{"gr", "ϊχώΩϋ", "ixwwu"},
-		{"Ell", "ϊχώΩϋ", "ixwwu"},
-		{"tr", "şüöğıçŞÜÖİĞÇ", "suogicsuoigc"},
+		{"de", "Wir mögen Bücher & Käse", "wir-moegen-buecher-und-kaese", true},
+		{"de", "Wir mögen Bücher & Käse", "Wir-moegen-Buecher-und-Kaese", false},
+		{"de", "Äpfel Über Österreich", "aepfel-ueber-oesterreich", true},
+		{"de", "Äpfel Über Österreich", "Aepfel-Ueber-Oesterreich", false},
+		{"en", "äÄäöÖöüÜü", "aaaooouuu", true},
+		{"en", "äÄäöÖöüÜü", "aAaoOouUu", false},
+		{"gr", "ϊχώΩϋ", "ixwwu", true},
+		{"gr", "ϊχώΩϋ", "ixwwu", false},
+		{"Ell", "ϊχώΩϋ", "ixwwu", true},
+		{"Ell", "ϊχώΩϋ", "ixwwu", false},
+		{"tr", "şüöğıçŞÜÖİĞÇ", "suogicsuoigc", true},
+		{"tr", "şüöğıçŞÜÖİĞÇ", "suogicSUOIGC", false},
 		// & fun.
-		{"de", "This & that", "this-und-that"},
-		{"en", "This & that", "this-and-that"},
-		{"es", "This & that", "this-y-that"},
-		{"fi", "This & that", "this-ja-that"},
-		{"gr", "This & that", "this-kai-that"},
-		{"ell", "This & that", "this-kai-that"},
-		{"Ell", "This & that", "this-kai-that"},
-		{"nl", "This & that", "this-en-that"},
-		{"pl", "This & that", "this-i-that"},
-		{"pol", "This & that", "this-i-that"},
-		{"tr", "This & that", "this-ve-that"},
-		{"test", "This & that", "this-and-that"}, // unknown lang, fallback to "en"
+		{"de", "This & that", "this-und-that", true},
+		{"en", "This & that", "this-and-that", true},
+		{"es", "This & that", "this-y-that", true},
+		{"fi", "This & that", "this-ja-that", true},
+		{"gr", "This & that", "this-kai-that", true},
+		{"ell", "This & that", "this-kai-that", true},
+		{"Ell", "This & that", "this-kai-that", true},
+		{"nl", "This & that", "this-en-that", true},
+		{"pl", "This & that", "this-i-that", true},
+		{"pol", "This & that", "this-i-that", true},
+		{"tr", "This & that", "this-ve-that", true},
+		{"test", "This & that", "this-and-that", true}, // unknown lang, fallback to "en"
 		// Test defaultSub, when adding new lang copy/paste this line,
 		// it contain special characters.
-		{"de", "1\"2'3’4‒5–6—7―8", "1234-5-6-7-8"},
-		{"en", "1\"2'3’4‒5–6—7―8", "1234-5-6-7-8"},
-		{"es", "1\"2'3’4‒5–6—7―8", "1234-5-6-7-8"},
-		{"fi", "1\"2'3’4‒5–6—7―8", "1234-5-6-7-8"},
-		{"gr", "1\"2'3’4‒5–6—7―8", "1234-5-6-7-8"},
-		{"nl", "1\"2'3’4‒5–6—7―8", "1234-5-6-7-8"},
-		{"pl", "1\"2'3’4‒5–6—7―8", "1234-5-6-7-8"},
+		{"de", "1\"2'3’4‒5–6—7―8", "1234-5-6-7-8", true},
+		{"en", "1\"2'3’4‒5–6—7―8", "1234-5-6-7-8", true},
+		{"es", "1\"2'3’4‒5–6—7―8", "1234-5-6-7-8", true},
+		{"fi", "1\"2'3’4‒5–6—7―8", "1234-5-6-7-8", true},
+		{"gr", "1\"2'3’4‒5–6—7―8", "1234-5-6-7-8", true},
+		{"nl", "1\"2'3’4‒5–6—7―8", "1234-5-6-7-8", true},
+		{"pl", "1\"2'3’4‒5–6—7―8", "1234-5-6-7-8", true},
 	}
 
 	for index, smlt := range testCases {
+		Lowercase = smlt.lowercase
 		got := MakeLang(smlt.in, smlt.lang)
 		if got != smlt.want {
 			t.Errorf(