Update dotenv-rails to version 2.6.0

Gemfile.lock

@@ -108,9 +108,9 @@ GEM
       activerecord (>= 3.0, < 5.3)
       delayed_job (>= 3.0, < 5)
     diff-lcs (1.3)
-    dotenv (2.5.0)
-    dotenv-rails (2.5.0)
-      dotenv (= 2.5.0)
+    dotenv (2.6.0)
+    dotenv-rails (2.6.0)
+      dotenv (= 2.6.0)
       railties (>= 3.2, < 6.0)
     email_validator (1.6.0)
       activemodel
@@ -142,7 +142,7 @@ GEM
     high_voltage (3.1.0)
     highline (2.0.0)
     honeybadger (4.1.0)
-    i18n (1.4.0)
+    i18n (1.5.3)
       concurrent-ruby (~> 1.0)
     i18n-tasks (0.9.28)
       activesupport (>= 4.0.2)
@@ -204,7 +204,7 @@ GEM
       thor (~> 0.19)
     newrelic_rpm (5.6.0.349)
     nio4r (2.3.1)
-    nokogiri (1.9.1)
+    nokogiri (1.10.1)
       mini_portile2 (~> 2.4.0)
     normalize-rails (4.1.1)
     oauth2 (1.4.1)