Tabulate dataset fields.
test_tabulate.py: In Python unittest 2nd arg expected.
tabulate.py: was not handling more than 2-column fields properly.
remove flake8 warnings on last commit.
refactor utf-8 encoding of SolveObject __repr__; refactor request debug logging
Merge pull request #57 from solvebio/feature/tabulate-dataset-fields

Tabulate dataset fields in printing (__str__). Closes #49
Rearrange the SolveObject tabulate code and integrate it with depository
versions and version dataset listings. Closes #5 and Closes #49
set paging=True as default;fixed index out of bounds exception;closes #52
implemented query.count();closes #50
better logging of warmup
implemented new 'limit' semantics and tests;closes #51;
Rebase dev on pg_hotfix
removed 'paging' kwarg
cleanup commented-out code
fixed failing test_cache
fixed bug where initial request was coercing to slice request
__getitem__ uses islice to do bounded fetch;code cleanup
removed print from test
improved semantics with limit and count;expanded test coverage;closes #61 #62;
fix tabulate first result in repr
clone query on count
fix how BatchQuery builds query params