Added tests to check for adding of dependencies

Checks for adding the dependency to the graph object and to the
rendered display
Fixed tests for adding a dependency

Note that adding a dependency affects the list of dependencies attached
to a concept object, so it needs to be reset before each test
Fixed removing dependencies tests

Note that transitions cause the edge not to be removed immediately
So we added a config setting to change the duration of transitions
Merge pull request #8 from knowledge-graph/more-tests

More tests