Kill 'goal' usage in the pants script.
Kill 'goal' usage in the pants script.

Testing Done:
Before this change:
```shell
$ rm -f pants.pex && ./pants >/dev/null | head -2
Building pants.pex to /home/jsirois/dev/3rdparty/pants/pants.pex...
WARNING: Specifying 'goal' explicitly is no longer necessary, and deprecated.
```
Now no more warning.

CI went green here: https://travis-ci.org/pantsbuild/pants/builds/49928198

Bugs closed: 1060

Reviewed at https://rbcommons.com/s/twitter/r/1738/

kwlzn/pants,gmalmquist/pants,megaserg/pants,gmalmquist/pants,laurentgo/pants,tdyas/pants,twitter/pants,foursquare/pants,sid-kap/pants,megaserg/pants,ericzundel/pants,laurentgo/pants,jessrosenfield/pants,pombredanne/pants,jtrobec/pants,mateor/pants,pombredanne/pants,manasapte/pants,dgomez10/xanon,baroquebobcat/pants,wisechengyi/pants,scode/pants,manasapte/pants,areitz/pants,wisechengyi/pants,fkorotkov/pants,scode/pants,di0spyr0s/pants,dbentley/pants,tdyas/pants,kwlzn/pants,ericzundel/pants,pantsbuild/pants,pgroudas/pants,ity/pants,megaserg/pants,baroquebobcat/pants,peiyuwang/pants,digwanderlust/pants,landism/pants,areitz/pants,jtrobec/pants,baroquebobcat/pants,jtrobec/pants,15Dkatz/pants,gmalmquist/pants,baroquebobcat/pants,di0spyr0s/pants,tdyas/pants,peiyuwang/pants,Gabriel439/pants,15Dkatz/pants,cevaris/pants,wisechengyi/pants,cevaris/pants,gmalmquist/pants,mateor/pants,wisechengyi/pants,pantsbuild/pants,twitter/pants,UnrememberMe/pants,scode/pants,UnrememberMe/pants,peiyuwang/pants,slyphon/pants,pgroudas/pants,dgomez10/xanon,benjyw/pants,fkorotkov/pants,Gabriel439/pants,qma/pants,scode/pants,pantsbuild/pants,fkorotkov/pants,jsirois/pants,peiyuwang/pants,qma/pants,dbentley/pants,dgomez10/xanon,UnrememberMe/pants,15Dkatz/pants,Gabriel439/pants,digwanderlust/pants,UnrememberMe/pants,slyphon/pants,landism/pants,sameerparekh/pants,gmalmquist/pants,peiyuwang/pants,slyphon/pants,landism/pants,Gabriel439/pants,dbentley/pants,tdyas/pants,jessrosenfield/pants,tejal29/pants,gmalmquist/pants,qma/pants,twitter/pants,ity/pants,pantsbuild/pants,Gabriel439/pants,lahosken/pants,pantsbuild/pants,twitter/pants,fkorotkov/pants,pombredanne/pants,sid-kap/pants,fkorotkov/pants,laurentgo/pants,benjyw/pants,qma/pants,pgroudas/pants,twitter/pants,TansyArron/pants,tdyas/pants,digwanderlust/pants,wisechengyi/pants,sameerparekh/pants,sameerparekh/pants,mateor/pants,laurentgo/pants,pombredanne/pants,dturner-tw/pants,UnrememberMe/pants,digwanderlust/pants,sameerparekh/pants,lahosken/pants,dgomez10/xanon,peiyuwang/pants,sameerparekh/pants,manasapte/pants,kslundberg/pants,jessrosenfield/pants,twitter/pants,TansyArron/pants,ericzundel/pants,cevaris/pants,jessrosenfield/pants,fkorotkov/pants,jessrosenfield/pants,mateor/pants,slyphon/pants,kslundberg/pants,TansyArron/pants,landism/pants,dturner-tw/pants,benjyw/pants,jtrobec/pants,jtrobec/pants,di0spyr0s/pants,foursquare/pants,wisechengyi/pants,15Dkatz/pants,mateor/pants,baroquebobcat/pants,pgroudas/pants,kwlzn/pants,manasapte/pants,ity/pants,dbentley/pants,baroquebobcat/pants,kwlzn/pants,kwlzn/pants,lahosken/pants,dturner-tw/pants,laurentgo/pants,kslundberg/pants,mateor/pants,dgomez10/xanon,benjyw/pants,landism/pants,areitz/pants,cevaris/pants,ericzundel/pants,benjyw/pants,landism/pants,digwanderlust/pants,landism/pants,sameerparekh/pants,tdyas/pants,foursquare/pants,kslundberg/pants,lahosken/pants,sid-kap/pants,tdyas/pants,megaserg/pants,wisechengyi/pants,15Dkatz/pants,pombredanne/pants,mateor/pants,ity/pants,manasapte/pants,TansyArron/pants,dturner-tw/pants,jtrobec/pants,areitz/pants,digwanderlust/pants,baroquebobcat/pants,peiyuwang/pants,pgroudas/pants,laurentgo/pants,fkorotkov/pants,dturner-tw/pants,dgomez10/xanon,pombredanne/pants,baroquebobcat/pants,dbentley/pants,cevaris/pants,qma/pants,manasapte/pants,foursquare/pants,TansyArron/pants,dturner-tw/pants,qma/pants,jsirois/pants,tejal29/pants,foursquare/pants,sid-kap/pants,kslundberg/pants,foursquare/pants,Gabriel439/pants,sid-kap/pants,dgomez10/xanon,foursquare/pants,slyphon/pants,twitter/pants,lahosken/pants,Gabriel439/pants,dgomez10/xanon,foursquare/pants,tdyas/pants,15Dkatz/pants,di0spyr0s/pants,scode/pants,dgomez10/xanon,qma/pants,mateor/pants,pombredanne/pants,pantsbuild/pants,lahosken/pants,areitz/pants,jessrosenfield/pants,benjyw/pants,foursquare/pants,fkorotkov/pants,slyphon/pants,tejal29/pants,benjyw/pants,tejal29/pants,cevaris/pants,wisechengyi/pants,dbentley/pants,lahosken/pants,pantsbuild/pants,areitz/pants,15Dkatz/pants,sameerparekh/pants,twitter/pants,megaserg/pants,UnrememberMe/pants,landism/pants,di0spyr0s/pants,ericzundel/pants,UnrememberMe/pants,gmalmquist/pants,tdyas/pants,kwlzn/pants,di0spyr0s/pants,dgomez10/xanon,areitz/pants,sid-kap/pants,ericzundel/pants,tejal29/pants,scode/pants,cevaris/pants,TansyArron/pants,manasapte/pants,lahosken/pants,kslundberg/pants,di0spyr0s/pants,dturner-tw/pants,jtrobec/pants,ericzundel/pants,twitter/pants,ity/pants,TansyArron/pants,sid-kap/pants,ity/pants,peiyuwang/pants,jsirois/pants,megaserg/pants,dbentley/pants,kslundberg/pants,scode/pants,ericzundel/pants,dgomez10/xanon,megaserg/pants,kwlzn/pants,15Dkatz/pants,jessrosenfield/pants,UnrememberMe/pants,ity/pants,pgroudas/pants,slyphon/pants,wisechengyi/pants,baroquebobcat/pants,UnrememberMe/pants