Remove dependency to XCode.

- Drop cocaine lib because it depends on gems that build native
  extentions (i.e. atomic).
- Call PlistBuddy via Backticks.
- Handle case when PlistBuddy exists non-zero.
- Remove XCode dependency from README.
- Bump version.
Merge branch 'no_xcode'

Conflicts:
	lib/wrapp/app_info.rb
	lib/wrapp/version.rb
	spec/wrapp/app_info_spec.rb