Added Kostas' functions from the hackathon; added ExecutionEnvironment member to Graph
fix merge conflicts with master
added execution environment to create calls in test
suppress warnings
fix conflicts with current master
empty test todos for implemented operations
fix count to work with Datasets of tuples, added test for numberOfVertices, numberOfEdges
static inner classes for getVertexIds, getEdgeIds, isWeaklyConnected, tests for former 2
isWeakly connected corrections and test
Added tests for addVertex, removeVertex, addEdge and union
Added removeEdge, added more tests
Fixed/added tests, based on Vasia's feedback
Fixed distinct vertex issues, changed removal filters
Merge pull request #1 from balidani/merge-Kostas-code

Added tests for addVertex, removeVertex, addEdge and union
added descriptions for add/remove methods
reorganized tests and readme
added vertex-centric iteration, removed pga
resolve merge conflicts
Merge pull request #9 from vasia/merge-Kostas-code

- Merge the code from Kostas' hackathon branch
- Daniel's work on graph mutation methods
- Vertex-centric iteration method