Merge pull request #117 from honkdamonk/master

Bugfix: Error in Map-Remove function
Merge pull request #118 from honkdamonk/master

Clearify what are functions for sequential/parallel context
Added a hand-written version of Dijkstra's shortest path to the test directory. Added comments to files requiring adjacency list format explaining the adjacency file schema.
adding mutatable priority map
mutatatble priority heap
adding prt q to gm.h
adding .gm file
implement function for parallel modification
added unit tests for some example algorithms (pagerank, hop_distance and kosaraju)