Remove double empty lines from docs

[vojtajina]

Currently google docs converts any single empty line into two empty lines when exporting into plain text.
This means that all empty lines are doubled in code examples.
We should trim them during fetching in the same way as we remove comments.
https://github.com/angular/angular.js/blob/master/gdocs.js#L72

[IgorMinar]

example: http://docs.angularjs.org/#!/tutorial/step_04

[IgorMinar]

Di should be able to handle this with right hand behind his back.