Adding bower.json so that build scripts dependent on the main attribute still work.

Many people are using your bower listing to include this awesome library into their projects, however, the repo has no `bower.json`.

This means that people who count on it being there for build scripts cannot use it as a true bower style dependency.

Usually, when a person wants to make a repo on bower, they run `bower init` This creates the `bower.json` with reasonable defaults. It is something that users count on being there. 

Addition of a `bower.json`, and in particular, the `main` attribute of the `bower.json`, ensures that people can use npm's like [main bower files](https://github.com/ck86/main-bower-files) to compile their source code without configuring which file is the actual source file in the repo.

The only issues I can think of by adding this are:
1. You will need to bump the version number in the `bower.json` when you make a new release.
2. You might want to point the `main` attribute at the minified version instead.