Fix linting errors in Tutorial/*

Tutorial/is_bitbar.sh

@@ -2,16 +2,19 @@
 
 # <bitbar.title>Is BitBar?</bitbar.title>
 # <bitbar.author>Mat Ryer and Tyler Bunnell</bitbar.author>
+# <bitbar.author.github>matryer</bitbar.author.github>
 # <bitbar.desc>Example script showing use of $BITBAR environment variable</bitbar.desc>
+# <bitbar.image>https://i.imgur.com/TcZJI06.png</bitbar.image>
 #
 # Example script showing how to let your scripts determine
 # whether they are expected to deliver BitBar output or not.
 #
 # Put this script in your BitBar plugins folder and notice
 # it says "In BitBar", but run it directly in Terminal, and it
 # says "In Terminal".
+BitBar=${BitBar}
 
-if [ $BitBar ]; then
+if [ "$BitBar" ]; then
   # this script is being called from within
   # BitBar.
   echo "In BitBar"

Tutorial/is_darkmode.sh

@@ -7,8 +7,9 @@
 # <bitbar.desc>Example script showing how to let your scripts determine whether OSX is in Dark Mode so you can adjust appearance. Must restart Bitbar after changing setting.</bitbar.desc>
 # <bitbar.dependencies></bitbar.dependencies>
 # <bitbar.image>http://i.imgur.com/2ark3Bq.png</bitbar.image>
+BitBarDarkMode=${BitBarDarkMode}
 
-if [ $BitBarDarkMode ]; then
+if [ "$BitBarDarkMode" ]; then
   # OSX has Dark Mode enabled.
   echo "Dark | color=white"
 else