ARROW-339: Python 3 compatibility in merge_arrow_pr.py
ARROW-339: Python 3 compatibility in merge_arrow_pr.py

Author: Wes McKinney <wes.mckinney@twosigma.com>

Closes #188 from wesm/ARROW-339 and squashes the following commits:

1f3617f [Wes McKinney] Remove cherry-picking cruft
6b99632 [Wes McKinney] Python 3 compatibility in merge_arrow_pr.py

jeffknupp/arrow,renesugar/arrow,laurentgo/arrow,pcmoritz/arrow,julienledem/arrow,StevenMPhillips/arrow,cpcloud/arrow,jeffknupp/arrow,siddharthteotia/arrow,laurentgo/arrow,wagavulin/arrow,jeffknupp/arrow,siddharthteotia/arrow,laurentgo/arrow,wesm/arrow,cpcloud/arrow,itaiin/arrow,cpcloud/arrow,TheNeuralBit/arrow,wagavulin/arrow,julienledem/arrow,yufeldman/arrow,icexelloss/arrow,laurentgo/arrow,julienledem/arrow,TheNeuralBit/arrow,apache/arrow,majetideepak/arrow,apache/arrow,kou/arrow,xhochy/arrow,renesugar/arrow,tebeka/arrow,wagavulin/arrow,NonVolatileComputing/arrow,NonVolatileComputing/arrow,pcmoritz/arrow,tebeka/arrow,itaiin/arrow,icexelloss/arrow,icexelloss/arrow,apache/arrow,apache/arrow,wesm/arrow,siddharthteotia/arrow,pcmoritz/arrow,dremio/arrow,majetideepak/arrow,xhochy/arrow,wagavulin/arrow,TheNeuralBit/arrow,pcmoritz/arrow,majetideepak/arrow,pcmoritz/arrow,wesm/arrow,yufeldman/arrow,majetideepak/arrow,pcmoritz/arrow,itaiin/arrow,itaiin/arrow,TheNeuralBit/arrow,StevenMPhillips/arrow,cpcloud/arrow,xhochy/arrow,xhochy/arrow,pcmoritz/arrow,jeffknupp/arrow,NonVolatileComputing/arrow,apache/arrow,StevenMPhillips/arrow,apache/arrow,renesugar/arrow,laurentgo/arrow,wagavulin/arrow,icexelloss/arrow,majetideepak/arrow,wagavulin/arrow,renesugar/arrow,wesm/arrow,wesm/arrow,dremio/arrow,xhochy/arrow,pcmoritz/arrow,tebeka/arrow,jeffknupp/arrow,NonVolatileComputing/arrow,cpcloud/arrow,pcmoritz/arrow,apache/arrow,kou/arrow,laurentgo/arrow,tebeka/arrow,laurentgo/arrow,jeffknupp/arrow,icexelloss/arrow,wagavulin/arrow,renesugar/arrow,julienledem/arrow,kou/arrow,wagavulin/arrow,apache/arrow,apache/arrow,dremio/arrow,siddharthteotia/arrow,icexelloss/arrow,majetideepak/arrow,siddharthteotia/arrow,cpcloud/arrow,tebeka/arrow,xhochy/arrow,xhochy/arrow,cpcloud/arrow,majetideepak/arrow,dremio/arrow,julienledem/arrow,julienledem/arrow,TheNeuralBit/arrow,itaiin/arrow,icexelloss/arrow,dremio/arrow,icexelloss/arrow,cpcloud/arrow,xhochy/arrow,kou/arrow,majetideepak/arrow,wagavulin/arrow,kou/arrow,jeffknupp/arrow,majetideepak/arrow,laurentgo/arrow,majetideepak/arrow,StevenMPhillips/arrow,icexelloss/arrow,siddharthteotia/arrow,laurentgo/arrow,julienledem/arrow,laurentgo/arrow,julienledem/arrow,StevenMPhillips/arrow,dremio/arrow,yufeldman/arrow,wesm/arrow,icexelloss/arrow,laurentgo/arrow,wagavulin/arrow,pcmoritz/arrow,icexelloss/arrow,majetideepak/arrow,wesm/arrow,kou/arrow,xhochy/arrow,laurentgo/arrow,yufeldman/arrow,renesugar/arrow,apache/arrow,xhochy/arrow,apache/arrow,renesugar/arrow,tebeka/arrow,cpcloud/arrow,pcmoritz/arrow,cpcloud/arrow,majetideepak/arrow,icexelloss/arrow,renesugar/arrow,itaiin/arrow,majetideepak/arrow,kou/arrow,julienledem/arrow,itaiin/arrow,NonVolatileComputing/arrow,siddharthteotia/arrow,wesm/arrow,jeffknupp/arrow,majetideepak/arrow,itaiin/arrow,yufeldman/arrow,laurentgo/arrow,kou/arrow,julienledem/arrow,pcmoritz/arrow,renesugar/arrow,tebeka/arrow,yufeldman/arrow,cpcloud/arrow,itaiin/arrow,renesugar/arrow,cpcloud/arrow,itaiin/arrow,xhochy/arrow,dremio/arrow,yufeldman/arrow,wesm/arrow,renesugar/arrow,NonVolatileComputing/arrow,apache/arrow,tebeka/arrow,kou/arrow,kou/arrow,renesugar/arrow,wesm/arrow,StevenMPhillips/arrow,cpcloud/arrow,NonVolatileComputing/arrow,pcmoritz/arrow,StevenMPhillips/arrow,siddharthteotia/arrow,kou/arrow,wesm/arrow,StevenMPhillips/arrow,apache/arrow,yufeldman/arrow,dremio/arrow,siddharthteotia/arrow,icexelloss/arrow,pcmoritz/arrow,pcmoritz/arrow,wesm/arrow,jeffknupp/arrow,apache/arrow,kou/arrow,xhochy/arrow,yufeldman/arrow,renesugar/arrow,laurentgo/arrow,itaiin/arrow,itaiin/arrow,dremio/arrow,xhochy/arrow,StevenMPhillips/arrow,TheNeuralBit/arrow,cpcloud/arrow,wesm/arrow,itaiin/arrow,xhochy/arrow,kou/arrow,itaiin/arrow,icexelloss/arrow,wesm/arrow,NonVolatileComputing/arrow,StevenMPhillips/arrow,majetideepak/arrow,tebeka/arrow,xhochy/arrow,itaiin/arrow,jeffknupp/arrow,jeffknupp/arrow,dremio/arrow,yufeldman/arrow,dremio/arrow,NonVolatileComputing/arrow,renesugar/arrow,NonVolatileComputing/arrow,siddharthteotia/arrow,wagavulin/arrow,NonVolatileComputing/arrow,yufeldman/arrow,siddharthteotia/arrow,renesugar/arrow,tebeka/arrow,wagavulin/arrow,laurentgo/arrow,kou/arrow