routing: Add some backwards compatibility support for parameter types. This makes it so old routes are still correctly formatting years/months/days which were previously hard-coded to int4/int2 types.

cov-core==1.15.0
coverage==4.0.3
invoke==0.12.2
mock==1.0.1
pytest==2.8.7
pytest-cov==2.2.1
pytest-mock==0.10.1