added npm and browserify support

[konsumer]

This adds proper dep-tracking, require, and exposes a main, so browserify (and probably webpack and other friends) will work. I also documented it in the README.

I tested this with browserify middleware, using this: https://gist.github.com/konsumer/0ed26b48e37118d9f89d

I might also recommend removing the postinstall line, as it's not needed for a clean npm install like this, and adds a bower dep and a little unneeded compile time.

[konsumer]

To make the npm install line work, you'll also need to publish it on npm, or you can instruct users to install with npm install --save brandly/angular-youtube-embed if you don't care about publishing to npm.

[axelson]

+1

[brandly]

@konsumer sorry for not getting to this sooner! you've been really active around this repo, and i haven't been keeping up :smile:

let me know what you think about those comments, and we'll get this sorted out