Fixed bug caused by non-iterable '0'.
Added calculate.py
Integrated calculate.py into hey.py.
Merge branch 'calculator' into jce-devel.
Fixed another bug.

For some reason, the Hey().parse() wasn't being passed in the command
line contents. Weird.
Merge pull request #7 from jce-devel/jce-devel

Bugfixes and calculator.py
Few more commands added to README