Get closer to actually executing the parser

Wrap `c::Struct_http_parser_settings` in `HttpParserSettings`.
Start working on tests
Merge remote-tracking branch 'nathan7/build'

Conflicts:
	Cargo.toml
Add clang includes to include path for bindgen
Merge remote-tracking branch 'nathan7/style'

Conflicts:
	src/lib.rs
fix build
simplify callback handling