Update release

Version bump

Uploading new version

Upgrade to 0.0.6

* Lua 5.3 compatibility.
* Use LuaRocks builtin build.

Fixing Lua dependency version

Bump version

Add Mac-only test for #22.

Make Buffer:add_utf8 support item_offset and item_length.

* Added `Buffer:get_length` which wraps `hb_buffer_get_length`.
* Added docs.
* Version bump.
* Fix #20.