* allow tests to run in random mode
* Fix random test mode for fiat-convert
* allow random test execution in persistence
* fix pep8 styling
* use "usefixtures" to prevent pylint "unused parameter" message
* add pytest-random-order to travis
* replace pymarketcap with coinmarketcap
* fix tests to use coinmarketcap instead of pymarketcap
* use arraypos 0
* update setup.py from pymarketcap to coinmarketcap
* Add test to check for unsupported Crypto currency
Result in a speed up of the unittest from 60s to 4s
Because it cost time to load Pymarketcap() every time we create
a CryptoToFiatConverter, it worth it to change it into a
Singleton.
