ARROW-2192: [CI] Always build on master branch and repository
ARROW-2192: [CI] Always build on master branch and repository

Author: Antoine Pitrou <antoine@python.org>

Closes #1634 from pitrou/ARROW-2192-always-build-on-master and squashes the following commits:

c7a87805 [Antoine Pitrou] ARROW-2192: [CI] Always build on master branch and repo [skip travis] [skip appveyor]

yufeldman/arrow,kou/arrow,kou/arrow,apache/arrow,apache/arrow,kou/arrow,laurentgo/arrow,renesugar/arrow,laurentgo/arrow,tebeka/arrow,laurentgo/arrow,icexelloss/arrow,kou/arrow,apache/arrow,apache/arrow,cpcloud/arrow,wagavulin/arrow,wagavulin/arrow,cpcloud/arrow,icexelloss/arrow,renesugar/arrow,wesm/arrow,apache/arrow,itaiin/arrow,majetideepak/arrow,wesm/arrow,itaiin/arrow,yufeldman/arrow,tebeka/arrow,apache/arrow,pcmoritz/arrow,apache/arrow,icexelloss/arrow,itaiin/arrow,wesm/arrow,pcmoritz/arrow,laurentgo/arrow,majetideepak/arrow,icexelloss/arrow,tebeka/arrow,dremio/arrow,wagavulin/arrow,pcmoritz/arrow,xhochy/arrow,dremio/arrow,tebeka/arrow,dremio/arrow,dremio/arrow,xhochy/arrow,laurentgo/arrow,laurentgo/arrow,xhochy/arrow,wagavulin/arrow,cpcloud/arrow,icexelloss/arrow,renesugar/arrow,renesugar/arrow,dremio/arrow,laurentgo/arrow,kou/arrow,itaiin/arrow,tebeka/arrow,wesm/arrow,majetideepak/arrow,icexelloss/arrow,wesm/arrow,yufeldman/arrow,yufeldman/arrow,pcmoritz/arrow,pcmoritz/arrow,icexelloss/arrow,icexelloss/arrow,laurentgo/arrow,cpcloud/arrow,majetideepak/arrow,laurentgo/arrow,apache/arrow,yufeldman/arrow,cpcloud/arrow,dremio/arrow,tebeka/arrow,icexelloss/arrow,itaiin/arrow,wesm/arrow,wesm/arrow,apache/arrow,wesm/arrow,cpcloud/arrow,xhochy/arrow,xhochy/arrow,itaiin/arrow,icexelloss/arrow,kou/arrow,itaiin/arrow,wesm/arrow,pcmoritz/arrow,cpcloud/arrow,laurentgo/arrow,xhochy/arrow,yufeldman/arrow,pcmoritz/arrow,kou/arrow,yufeldman/arrow,dremio/arrow,yufeldman/arrow,yufeldman/arrow,renesugar/arrow,renesugar/arrow,majetideepak/arrow,wagavulin/arrow,wagavulin/arrow,wagavulin/arrow,pcmoritz/arrow,itaiin/arrow,cpcloud/arrow,cpcloud/arrow,xhochy/arrow,renesugar/arrow,kou/arrow,itaiin/arrow,icexelloss/arrow,xhochy/arrow,majetideepak/arrow,tebeka/arrow,apache/arrow,renesugar/arrow,laurentgo/arrow,dremio/arrow,majetideepak/arrow,yufeldman/arrow,dremio/arrow,kou/arrow,majetideepak/arrow,cpcloud/arrow,xhochy/arrow,pcmoritz/arrow,xhochy/arrow,icexelloss/arrow,pcmoritz/arrow,apache/arrow,itaiin/arrow,itaiin/arrow,wagavulin/arrow,renesugar/arrow,renesugar/arrow,itaiin/arrow,xhochy/arrow,wagavulin/arrow,cpcloud/arrow,pcmoritz/arrow,pcmoritz/arrow,xhochy/arrow,pcmoritz/arrow,tebeka/arrow,wagavulin/arrow,renesugar/arrow,xhochy/arrow,kou/arrow,dremio/arrow,apache/arrow,cpcloud/arrow,itaiin/arrow,majetideepak/arrow,apache/arrow,dremio/arrow,laurentgo/arrow,itaiin/arrow,kou/arrow,majetideepak/arrow,wesm/arrow,tebeka/arrow,icexelloss/arrow,wesm/arrow,pcmoritz/arrow,laurentgo/arrow,xhochy/arrow,wagavulin/arrow,kou/arrow,tebeka/arrow,pcmoritz/arrow,xhochy/arrow,wesm/arrow,majetideepak/arrow,laurentgo/arrow,majetideepak/arrow,apache/arrow,icexelloss/arrow,majetideepak/arrow,itaiin/arrow,wesm/arrow,renesugar/arrow,kou/arrow,yufeldman/arrow,kou/arrow,majetideepak/arrow,renesugar/arrow,wesm/arrow,cpcloud/arrow,laurentgo/arrow,cpcloud/arrow,renesugar/arrow,renesugar/arrow,majetideepak/arrow,wagavulin/arrow