Parse dates and timestamps

[vrajmohan]

#83 adds the ability to parse data types like ints, floats and bools. These were trivial to implement as pandas supports them well. I can see a case for supporting dates and timestamps as well. This will take more effort as pandas does not support them well - dates are not supported at all, timestamps are not automatically detected but need to to be specifically indicated in the read_csv call.

This would be a requirement in an API that supported query for the most recent n resources.