Added TmxVec4 and changed loadMask

Made loadMask return a vector 4 (TmxVec4) of the coords of the grid
tiles it marked "true", along with the width and height of the tiles.
This allows external physics engine usage as well as manual entity
placement.
Merge pull request #9 from ShaneK/master

Added TmxVec4 and changed loadMask
Merge pull request #24 from squiddingme/master

Add support for Haxepunk's new SlopedGrid mask
Adding 'has' function to TmxPropertySet to check whether a property exists.
Merge pull request #25 from bendmorris/master

Adding 'has' function to TmxPropertySet to check whether a property exists
don't expose Map abstract, can cause clashes with Map type
Graphiclist now receives Array<Graphic> not Array<Dynamic>
Merge pull request #28 from Roger/fix_map_clashes

don't expose Map abstract, can cause clashes with Map type
Merge pull request #29 from Roger/fix_debug_with_haxepunk_dev

Graphiclist now receives Array<Graphic> not Array<Dynamic>