Remove _entity from Graphic, adding renderAtlas method, fixes #197
adding renderAtlas to Graphiclist
Setting Graphiclist.blit on first addition
Adding changes for 2.5.0
license change
Should not destroy graphic when entity is removed, because graphic object maybe shared.
TravisCI: Use $TRAVIS_BUILD_DIR instead of hard-coded path.
Merge pull request #205 from andyli/travis

TravisCI: Use $TRAVIS_BUILD_DIR instead of hard-coded path.
Merge pull request #206 from andyli/no-auto-graphic-destroy

Should not destroy graphic when entity is removed