Remove unneeded jslint flag in "gulpfile.js"
Simpler initialization of "file.jslint.data"
Use more recognizable callback pattern in "report.js"

- Before: "cb(undefined, value)"
- Now, more typical: "cb(null, value)"
Early exit from "jslint.run" when invalid file is received
Do not re-analyse file if already analysed
Simpler ".npmignore"
Merge pull request #6 from pandell/allow-jshintchaining

Allow JSHint chaining