Update to target libmarquise 2.0.4

libmarquise has changed a bit under the hood, so pymarquise requires a bump to catch up. This was originally going to be more substantial, but the changes to the marquise_ctx struct ended up being minimal.

The biggest change was hauling GLib headers so CFFI can look up definitions when it compiles the binding shim.

GLib is really annoying
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The headers need to be available, but they could be located anywhere, depending on your distro. The stuff I've coded in works for me (Fedora 20), and will probably fail anywhere else unless you patch things up. :(