[TIMOB-13908] Fixed several areas where config and session files are not writable. Added isFileWritable() function to fs lib. Improvements to AppcException.
Merge pull request #48 from appcelerator/timob-13908

[TIMOB-13908] Fixed several areas where config and session files are not...
Merge branch 'master' of github.com:appcelerator/node-appc