added pickle method for quantity
added test for pickleability of quantity.
added is comparison and some pep 8 changes.
autopep8ed
un-autopep8ed the URL as to @astrofrog's request
un-autopep8ed another URL as to @astrofrog's request
un-autopep8ed another URL as to @astrofrog's request
Merge pull request #1325 from wkerzendorf/units/quantity_pickleable

Make Quantities pickleable again