WIP support Buffer::Use

[trevnorris]

There may be cases where a user wants to use the original char* instead
of making a copy of the data. This adds support for the new Buffer::Use
method, while creating a shim for pre-v0.11.

Once a name has been approved I'll also add entries into the README.

I'm not sure what an appropriate name for this method should be, hence the ridiculous name. :)

[rvagg]

yeah, this is nice, merge it with the 0.2.0 branch though and docs will be interesting--I'll probably use this myself in a few places.

re naming, I'm all for crazy names but "mother" might not be a bit too much of a distraction. Perhaps "original", "source", or maybe even just NanBufferUse() to match up with Buffer::Use()?

[trevnorris]

Hah. The ridiculous name was intentional as a reminder to have it changed. NanBufferUse() sounds good. I'll update with that and add the docs to the README.

[trevnorris]

@rvagg I switched this over to the 0.2.0 branch, hence all the extra commits. Please take another look at 7ec7337 to make sure style and wording are adequate.

[rvagg]

very nice

[rvagg]

I've merged this in to 0.2.0, see #6. I had to add a static inline for FreeData to not get linking errors when using nan.h in multiple files.