Fix some stuff with Map.to_xml with optional parameter and add Terrain handling
Docs for Tileset::load_xml
Merge pull request #5 from Quintus/add-tileset-from-file

Docs for Tileset::load_xml
fixes some stuff, make the objects copyable
Merge branch 'master' of github.com:Hanmac/tmx-ruby
add next_first_gid into Map class
Merge remote-tracking branch 'upstream/master'

Conflicts:
	lib/tiled_tmx/tileset.rb