Merge pull request #29 from mitchmindtree/master

Changed get_info to return Result and made sample_format method public.
Merge pull request #32 from mitchmindtree/master

Cleaned up example, generalised output buffer parameter and improved return types on get_stream_read/write_available.
Merge pull request #34 from mitchmindtree/master

Publicly expose 'Error' in pa/mod.rs and added more useful trait bounds to SamplePrivate
Merge pull request #35 from mitchmindtree/master

Added operator traits to SamplePrivate
Updated to latest Rust and Cargo