add RubyUnits namespace to Unit
Don't load 'Unit()' helper if only loading namespaced code.  Add travis config for 2.0.0
Version bump to 1.4.4
update readme with information about namespaced classes and how to use them.

See #60
add another caveat about the Unit helper
Merge pull request #76 from olbrich/namespace

Namespace support, closes #60