clean-up + variadic hex file line data lenght + test

Hi,

I have cleaned IHex a bit and added support for setting number of bytes encoded per hex file line (1-255). I also added trivial test case. Please pul if looks interesting enought.
Create new egg to http://pypi.python.org/pypi/IHex/ would by nice too.

There is small issue with versions, on pypi is available v 0.1.3, but on github only 0.1.1, can by this fixed please?