v0.13.0

Python 3.7 support

• Remove Python 3.6 from Pipfile (allows Python 3.7)
• Add Python 3.7 on README

General

• Multiple error keys can raise an InvalidResponse
• Improve README
• Updated dependencies
• Pipenv support on pyup

Buda

• Fix typo on LTC currency constant (it had PEN as value)
• Add pagination support for deposits and withdrawals on Buda
• withdrawals and deposits accept page and per_page params
• New withdrawal_pages and deposit_pages methods includes pages meta obj
• Remove UNTESTED note on withdrawals