Move Graph::hasEdgeParallel() to new Algorithm\Parallel
Move parallel edges algorithm helpers to Algorithm\Parallel
Ignore coverage for unreachable code
Add (failing) test with 100% coverage for Algorithm\Parallel
Simplify and fix getting parallel edges of undirected edges
Document new Algorithm\Parallel
Document fixed multiple parallel edges
Merge pull request #52 from clue/move-algo-parallel

Move parallel edges algorithms to new Algorithm\Parallel