Code and coverage improments part II

.circleci/config.yml

.coverage.t430s.7808.287497

.coveragerc

beem/transactionbuilder.py

beembase/memo.py

beemgraphenebase/account.py

beemgraphenebase/base58.py

beemgraphenebase/ecdsasig.py

beemgraphenebase/signedtransactions.py

beemgraphenebase/types.py

docs/requirements.txt

setup.py

tests/beemgraphene/test_account.py

tests/test_account.py

tests/test_block.py

tests/test_blockchain.py

tox.ini