support for tracking new file additions in newly created folders
updated mkdirThenAddFile
using fs.mkdirSync instead of grunt.file.write in mkdirThenAddFile. Closes GH-53.

grunt.file.write seems to mask gaze's inability to recognize newly added files
in newly created folders. also simplified mkdirThenAddFile by removing assertion for tmp.js
adding test case for grunt.file.write