Add deploy task in gulpfile.js (#39)

This PR addresses two things 
1. #39 by adding a `deploy` task to `gulpfile.js`
2. Update package.json

The gulp task `deploy` (using [gulp-gh-pages plugin](https://github.com/rowoot/gulp-gh-pages/blob/master/index.js)) does the following:
1. Clone remote repo
2. Checkout `gh-pages` branch (create if it doesn't exist)
3. Copy files specified in `gulp.src`
4. Add files (if no new changes are detected, it stops here)
5. Commit with message "Updates"
6. Push to remote

The task looks as below.
````
gulp.src([])
.pipe(deploy(gitRemoteUrl, remote) // plugin emits the files for further piping
````

Again, feedback appreciated.