Tx refactor clean-up

[ryanio]

This PR accomplishes a few housekeeping tasks left over from #812:

• Removes an extra added console.log
• Adds additional documentation for tx.sign to highlight that only the returned Transaction is signed
• Re-adds TxOptions to behave more similarly to other packages

[codecov]

Codecov Report

Merging #887 into master will decrease coverage by 0.12%.
The diff coverage is 91.66%.

Flag	Coverage Δ
#account	92.85% <ø> (ø)
#block	76.65% <75.00%> (-0.17%)	⬇️
#blockchain	80.13% <ø> (-0.32%)	⬇️
#common	93.19% <ø> (ø)
#ethash	82.22% <ø> (-1.12%)	⬇️
#tx	93.08% <100.00%> (+0.13%)	⬆️
#vm	88.16% <ø> (-0.04%)	⬇️

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[holgerd77]

LGTM