Nomics-python

Previously, Currencies.get_currencies only returned data for the first currency id in a list (if given). This bug is now resolved.

* Removed logic to format dates
* Combined Aggregated Pair, Aggregated, and Exchange candles
* Implemented more Enhanced (paid) methods

Refactored wrapper by adding modularity.

Added
* get_all_time_highs
* get_supplies_interval
* get_currencies_interval
* Travis CI integration