Support presto Decimal, Date and Timestamp types

[devinstevenson]

Hi @jingw.

I added support on Presto for decimal, date, and timestamp presto types. I also modified the tests to include a date type. The Travis CI test failed on python 3.6 seems to be a Travis CI issue. The tests passed on all other versions of python.

[codecov-io]

Codecov Report

Merging #171 into master will decrease coverage by 0.24%. The diff coverage is 97.56%.

@@            Coverage Diff             @@
##           master     #171      +/-   ##
==========================================
- Coverage   95.71%   95.47%   -0.25%     
==========================================
  Files          14       14              
  Lines        1422     1457      +35     
  Branches      147      149       +2     
==========================================
+ Hits         1361     1391      +30     
- Misses         40       44       +4     
- Partials       21       22       +1

Impacted Files	Coverage Δ
pyhive/tests/test_hive.py	97.7% <ø> (ø)	:arrow_up:
pyhive/tests/test_presto.py	96.36% <ø> (-3.64%)	:arrow_down:
pyhive/tests/test_sqlalchemy_hive.py	100% <100%> (ø)	:arrow_up:
pyhive/presto.py	94% <100%> (+0.38%)	:arrow_up:
pyhive/tests/test_sqlalchemy_presto.py	100% <100%> (ø)	:arrow_up:
pyhive/sqlalchemy_presto.py	91.97% <95.45%> (+0.59%)	:arrow_up:
pyhive/hive.py	90.09% <0%> (ø)	:arrow_up:

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