Add subclass hook for additional data transformation to Presto cursor class.

[jezdez]

This is a follow-up of #82 which proposed a backward-incompatible change for the strucutre of data returned by the Presto cursor and simplifies doing additional data transformation without having to override the majority of the response processing method.

The purpose of this is being able to extend Redash's (https://redash.io) Presto query runner to show more human-readable query results.

I've signed the Dropbox CLA.

[codecov-io]

Codecov Report

Merging #222 into master will decrease coverage by 0.06%. The diff coverage is 88.88%.

@@            Coverage Diff             @@
##           master     #222      +/-   ##
==========================================
- Coverage   93.94%   93.88%   -0.07%     
==========================================
  Files          14       14              
  Lines        1487     1504      +17     
  Branches      159      159              
==========================================
+ Hits         1397     1412      +15     
- Misses         64       66       +2     
  Partials       26       26

Impacted Files	Coverage Δ
pyhive/presto.py	93.7% <100%> (+0.08%)	:arrow_up:
pyhive/tests/test_presto.py	98.4% <86.66%> (-1.6%)	:arrow_down:

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update d19cb0c...8ed1864. Read the comment docs.

[jezdez]

@gsilk Hey there, I was wondering if there is anything else needed for this to be reviewed?

[jezdez]

Is anyone else interested in reviewing this at Dropbox?

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}