Added verbose functionality to is_compatible
Separated changes into a separate function
diff() method moved to a independent helper function
Added optional string_io argument
Object changed from string IO to file-like
moved to utils, name changed and PEP8 complient.
=New line removed from docstring
Now with unit tests
Unit tests modified to use ref files
Minor spelling/testing fixes

duplicate str_repr files removed and test fixes
str_repr files reinstated
str_repr reinstated properly