Don't add dist files to repo
flake8 tidy
Minor coding improvements
Decimals rather than floats
Thread safety and better auth init

Auth parameters now parsed in APIPrivateCall.__init__

Calls are now threadsafe if they are reused (by removing stateful
parameters).
Convert unix timestamps to datetime objects
Update documentation for api data type changes
Convert date strings to datetime too
Merge pull request #2 from SmileyChris/master

Internal changes, better datatypes