mention 2.1 changes
Merge branch 'master' of github.com:HipByte/RubyMotionDocumentation
modify 2.1. Common Options - xcode_dir description
Merge pull request #24 from amazedkoumei/master

modify "2.1. Common Options - xcode_dir" description
Merge branch 'refs/heads/master' into japanese

Conflicts:
	guides/project-management/index.txt