Feature: Add function to check if localRIB contains a given path and prefix combination. (#11)

* Add a ContainsPfxPath method to LocRIB to check if a route exists already.
* Check for nil pathes in compare
* Add myself to CONTRIBUTORS and AUTHORS
* Added docs
* Avoid segfault on nil and remove shaddowing of keyword new
* Make route == nil useful
* Update loc_rib.go