Several bug fixes and improvements

After working on ember-cli-bootswatch, I discovered several issues with the latest release of this addon. This PR fixes several bugs and adds some improvements:

* `importBootstrapCSS` and `importBootstrapFont` option conditions in `index.js` were incorrect. Basically was the opposite of the option name, fixed and also enabled backwards compatibility if the options were not included from the projects `Brocfile.js`
* Version 0.0.13 currently does not work, error about "unknown shim.js" file. Not sure were that file is supposed to be or what it is so I simply removed the import. Fixes #35 
* Also `.import()` the minified version of several files for production builds. Since the bower deps include minified versions, I've typically included them.
* Removed the `.map` files from being imported in production builds. They are not needed and are not referenced in the minified stylesheets.
* Moved the theme import _after_ the standard bootstrap stylesheet. This way the theme styles will override the standard styles.
* Fixed an unreported bug where the `bootstrap_for_ember` components were being imported twice. Because there is a file for both max and min, the previous `readdir()` was including the filename twice, therefore imported twice.
* Used a new feature of ember-cli 0.1.2 that installs multiple bower deps in one call, reducing overhead.

I'd suggest at least fixing the shim.js error and incorrect option conditions. Then release a new version since the current version of this addon is un-usable. Thanks for your consideration!