Initial setup using a C extension.

While I've tried to keep Oga pure Ruby for as long as possible the performance
of Ragel's Ruby output was not worth the trouble. For example, lexing 10MB of
XML would take 5 to 6 seconds at least. Nokogiri on the other hand can parse
that same XML into a DOM document in about 300 miliseconds. Such a big
performance difference is not acceptable.

To work around this the XML/HTML lexer will be implemented in C for
MRI/Rubinius and Java for JRuby. For now there's only a C extension as I
haven't read up yet on the JRuby API. The end goal is to provide some sort of
Ragel "template" that can be used to generate the corresponding C/Java
extension code. This would remove the need of duplicating the grammar and
associated code.

The native extension setup is a hybrid between native and Ruby. The raw Ragel
stuff happens in C/Java while the actual logic of actions happens in Ruby. This
adds a small amount of overhead but makes it much easier to maintain the lexer.
Even with this extra overhead the performance is much better than pure Ruby.
The 10MB of XML mentioned above is lexed in about 600 miliseconds. In other
words, it's 10 times faster.
Use rb_enc_str_new instead of rb_enc_str_new_cstr.

The latter in combination with strndup() would leak large amounts of memory.
Docs for the C lexer.
Docs for the Ruby part of the XML lexer.
Removed unused YARD tag.
Use liboga as a prefix in the C code.

Namespaces? What are those?
Half-assed JRuby boilerplate.

Blowing my brains out over getting this fat pig to do what I want but we're
getting there.
Merge branch 'native-ext' of github.com:YorickPeterse/oga into native-ext
Corrected various extension paths.
Updated the list of files to clean.
Use 4 spaces for C/Java code.
Don't track the generated Java lexer.
Removed Cliver as a dependency.

Since I'm not using any Ragel version specific features it's not really needed
to check for the version.
Setup for Java and Ragel.
Remove the Java output when cleaning.
Removed unused cliver require.

Dumbass.
Removed Cliver from the parser task.
Setup Ragel for JRuby and load things the hard way
Slap JRuby so that it can load the .jar file.
Removed the package line in LibogaService.java