README.rst: Fixed travis image reference.
README.rst: Fixed travis image reference.

jscinoz/assetgraph,slang800/assetgraph,assetgraph/assetgraph,papandreou/assetgraph,papandreou/assetgraph,jscinoz/assetgraph,jscinoz/assetgraph,slang800/assetgraph,papandreou/assetgraph