addresses issue #2 among other things

- removed `bower_components` from version control
- updated & moved `ng-prettyjson.html` into `demo/` directory
- added `.bowerrc` to specify `lib` as Bower directory
- added `lib` to `.gitignore`
- further split up `ng-prettyjson.js` for ease of unit testing
- better performance when making entities
- added tests for `markup()` and `makeEntities()` functions
- updated `travis.yml` to use `grunt-cli`
- updated `Gruntfile.js` to have `unit` and `continuous` targets for test; `unit` will run and watch for updates while `continuous` is best used by Travis
- renamed `MIT-LICENSE.txt` to standard LICENSE for Bower/NPM
- updated test script of `package.json` to use Grunt

note: unless you want to run Karma directly by some other means, with `grunt-karma`, the `karma.conf.js` file(s) are probably not needed.  I haven't removed them, because other IDEs (like JetBrains products) can run Karma directly if given a configuration file, but cannot do this w/ Grunt.