Can now specify that a property should be treated as a number by
checking the box.

If it can't be cast as a number (more specifically an integer) it will
be stored as a string
Can now filter by label(s)
Only show labels that are actually in use
Node add/delete/update refreshes label list

Also, refactoring
Layout tweakery to get the graph next to the filter/graph refresh stuff
Updated README to have some better usage information
Silly GFM
Merge pull request #4 from jgillmanjr/development

Development into Master