Sourcemap combination and better map granularity

Resolves #79.
Add angular.js to the ng-annotate repo instead so we can avoid the devDependency. The file should then get removed in the prepare script so it doesn't end up on npm, similar to https://github.com/olov/ng-annotate/blob/66885c6bb1f4406e848941e18db21f637802afeb/build/prepare.sh#L11