Clean up .gitignore

.gitignore

@@ -16,22 +16,6 @@
 # Ignore Byebug command history file.
 .byebug_history
 
-## Specific to RubyMotion:
-.dat*
-.repl_history
-build/
-*.bridgesupport
-build-iPhoneOS/
-build-iPhoneSimulator/
-
-## Specific to RubyMotion (use of CocoaPods):
-#
-# We recommend against adding the Pods directory to your .gitignore. However
-# you should judge for yourself, the pros and cons are mentioned at:
-# https://guides.cocoapods.org/using/using-cocoapods.html#should-i-check-the-pods-directory-into-source-control
-#
-# vendor/Pods/
-
 ## Documentation cache and generated files:
 /.yardoc/
 /_yardoc/
@@ -45,9 +29,9 @@ build-iPhoneSimulator/
 
 # for a library or gem, you might want to ignore these files since the code is
 # intended to run in multiple environments; otherwise, check them in:
-# Gemfile.lock
-# .ruby-version
-# .ruby-gemset
+Gemfile.lock
+.ruby-version
+.ruby-gemset
 
 # unless supporting rvm < 1.11.0 or doing something fancy, ignore this:
 .rvmrc