start TMS implementation
"EPSG:900913" is the same as "OSGEO:41001", "EPSG:3785", "EPSG:3857" or "EPSG:54004"
get layer metadata
 move TileMap into a seperate class
implement gettile and items method for TileMapService
items can be filtered by profile and srs
make it a doctest
make tms.txt tests pass
comment out change for testing with python setup.py test
Merge pull request #50 from cleder/master

TMS support
add Christian (TMS)