move reading of CSV export to separate function
docstring formatting
create new class for WingJ objects

this structures the code a lot better as it splits up the individual parts of
the calculations into smaller, better documented and thus more maintainable
methods of the newly created class
new "imagej" submodule for "volpy"
move WingJStructure class to "volpy.imagej" module
update docstrings
add note about DictReader()