Collaboration analysis with Features.

This pull request basically adds support for collaboration analysis with features instead of functions.
The analysis can be enabled with a new parameter "--collaboration", which can have the 3 values `function`, `feature_file` and `feature`

### `function`

Everything should be as it was before

### `feature_file`

Uses the same analysis logic as `function` but with `#ifdef` borders instead of functions.

### `feature`

> (SUM(MIN(line-changes of author1 on feature, line-changes of author2 on feature) FOR feature IN features))

This is basically the formula we use for measuring the collaboration strength between two authors between two releases.
This is done pretty straightforward by first filtering for interesting lines, then summing up the number of lines every author worked on a feature and then calculating the above sum.

Additionally I fixed some typos and updated nodejs. There are also Unit Tests for the parser of the cppstats outpuf file!