Support onBuildRead option

To support Angular.JS one has to prevent uglifier destroying the function arguments for dependency injection. One solution is to convert those arguments into a different uglier syntax that will prevail uglification. onBuildRead needs to be passed to r.js as a literal function, not a string that's what this pull request does.

Example usage:
```YAML
modules:
  - name: 'application'
onBuildRead: "function (moduleName, path, contents) { return require('ng-annotate')(contents, {add: true}).src;}"
```
requires installing ng-annotate
`npm-install -g ng-annotate`