Remove angular-base64.min.js from main section to avoid double insert by grunt

Hi, thanks for the lib, after I've installed it and ran: ```grunt bower-install``` I got 2 new entries to my index.html
```
    <script src="bower_components/angular-base64/angular-base64.js"></script>
    <script src="bower_components/angular-base64/angular-base64.min.js"></script>
```
This is because there are 2 files declared in the main section of .bower.json if I remove angular-base64.min.js from the config and run  ```grunt bower-install``` in my index.html I only get ```<script src="bower_components/angular-base64/angular-base64.js"></script>```

Many thanks