Refactor utils.py into a subpackage

Created a subpackage for utils and moved utils.Validate and
utils.Count classes as separate submodules under it. This refactoring
was done following pylint's advice.
Add license to utils package and remove TODO from avro.py

Better use Issue queue to keep track of what's to be done
Add pylint test for Travis and update MANIFEST.in

This is an experimental test to see if Travis handles pylint
testing. At this commit, pylint gave code rating 10.0/10.0 for the
code on my computer.