Bug/02 angular issues

This PR includes some changes to the Grunt file configuration in order to improve the performance loading remote files (js and css).

I couldn’t reproduce the original problem, but I think this PR will fix it ( fixes #960 ).

### In summary:

* Width attributes for img tags
* Changes in Grunt config file. (see bellow)
* Min css files
* All vendors js in a single file (except zeroclipboard).
* Controllers, services and initial files for Copay in a single file. (except models/)
* Updated README.

### Grunt

There are three main modes for run Grunt: 

1. grunt (for development, with --target=dev by default)
2. grunt prod (for production environment, compressed, without --target)
3. grunt watch (auto compilation if any file is modified)

### Note

Please, check if you have this problem #960