Merge pull request #8 from msabramo/tox

Add tox.ini; make .travis.yml use it
Added coverage reporting.

In the process, I removed tox as it made things so much more complex for me.
Delay importing sys.getrefcount until needed

This makes it possibly to at least install on PyPy

Addresses: GH-4 ("pypy compatibility")
Merge pull request #9 from msabramo/delay_sys_getrefcount_pypy

Delay importing sys.getrefcount until needed