Add task "export-filerev" and packge.json file
Rename function name and variable name
1) Read src files as buffer, instead of as string;
2) Use "readable", "end" events to achieve reading from stream, and use "update", "digest" methods to achieve calculating hash;
Filter directories out by config, not do this internally
Support export revision in what digit
Internal log before exporting to outside
Export revision in `grunt.config()` with key "taskName:targetName"
Add verbose log
Change log api
Use "bind-args" package to bind arguments, but not bind `this`
git ignore OS X temporal files
1) Access all `src` files by `this.filesSrc`, because this task is read only and doesn't care about destination file paths;
2) Callbacks `onFileDone` and `onAllFilesDone` support asynchronize operation;
Fix invalid "files" field
Add keywords
Not support radix of revision so far
Update package description
Add test run by grunt
Add README doc
Update package's version