temperature version 1.2 has been released!

Temperature makes it easy to deal with temperatures in Ruby, but
adding mixin methods to numbers and strings.

This was inspired by using Ruby to manipulate data from my home
weather station, and wanting it to keep track of the units for me so
that I didn't have to think about that in code.

Changes:

### 1.2 ===
* 2 minor bug fix
* fix rakefile to do readme correctly
* fix a warning (thanks to Matt Nelson)
* 1 major enhancement
* Add Rankine units (thanks to Matt Nelson)