feat(stoplight): Validation Service

This PR converts Deuce to make use of stoplight
(https://pypi.python.org/pypi/stoplight)

All the validation rules have been restructured, Especailly those around
markers and limits.
rm: test_rules was removed as it was not actually testing Validation Rules
Merge pull request #184 from TheSriram/import_stoplight

feat(stoplight): Validation Service