String encodings

[kkoopa]

This is for #3.

[kkoopa]

It would be nice to have a proper test suite. Please test and fix.

[rvagg]

yeah, I've been thinking how to do a test suite on all this, it's all getting way more complicated than I imagined.

[kkoopa]

@trevnorris Could you have a look at this? I am not sure on when zero terminators need to be added, e.g. should buffers get an extra terminating zero? Also, what about the external buffer, will that work as is, or do I need to get at it through ->data()?

[trevnorris]

@kkoopa added a few comments.