rename README to README.md so that the github can render it correctly
Added halide_opengl_output_client_bound() to allow the app to specify that Halide should not bind output render targets
Update make distrib for README.md

`make distrib` was looking for the non-existent file "README", which was renamed to "README.md" by commit 9fc6c65
Add include for msvc 2010 (fixes #428)
Fixed variable naming and spacing
Updated internal_assert and switched coordinate calculation to scalar code