Improved APIError Message

[ericpassmore]

Added internal nodeos message returned to clients when API errors are returned. Fixes #32

• Returning detailed message and summary when it exists
• Added test case
• Added mock data

[ericpassmore]

Investigating tracking down one item before ready to submit. get_transaction now requiring type conversion in tests

• was id now id.hexstring
• was block_num now Number(block_num)

[ericpassmore]

Closing this pull request. Moving the discussion on best path forward back to issue #32