Feature enhansement

Okay, a closer reading of RFC-4122, plus looking at some other UUID
implementations lead me to modify the v1 behavior a bit.  It's *mostly* a
backward compatability, although the C API changes just slightly.  As such,
I'm calling it a minor version increment (http://semver.org/) since not many
people are using this.

Anyway, uuidlib_v1() now takes a "clock sequence" value, if negative, a
random value is used; otherwise, the given "clock sequence" is used.
Update the rockspec filename, and a clarification in the README.