Provide an option to skip path resolution

[nimrod-becker]

Considering aggregating coverage reports on the same code, but from different installations or locations, linux installation and windows installation for example. In such cases, if the source files would appear under different paths their coverage won't be aggregated into a single asset, but rather would appear per each unique path.

Provide an option to skip path resolution and work with the provided paths (relative in the mentioned case) thus enabling aggregation.

See #90

[SBoudrias]

If it works without calling path.resolve, why offering the option at all?

[nimrod-becker]

Only reason I thought of was backward compatibility, but if you don't find it that important, can easily be removed.

[SBoudrias]

Yeah, let's just remove it!

[nimrod-becker]

Are we going ahead with it ?

[SBoudrias]

Yes, I didn't see you pushed a new diff (github doesn't notify you when it happen).

Thanks for sending the PR!