Bug 931310: Further improve New Relic deploy ping.
Bug 931310: Further improve New Relic deploy ping.

* Move revision.txt handling to update instead of pre_update.
* Get a real change log instead of just a github url.
* Steal wonderful description code from chief-james (willkg)

TheoChevalier/bedrock,davehunt/bedrock,glogiotatidis/bedrock,hoosteeno/bedrock,bensternthal/bedrock,mermi/bedrock,alexgibson/bedrock,petabyte/bedrock,andreadelrio/bedrock,rishiloyola/bedrock,Jobava/bedrock,analytics-pros/mozilla-bedrock,schalkneethling/bedrock,CSCI-462-01-2017/bedrock,sylvestre/bedrock,Jobava/bedrock,dudepare/bedrock,ericawright/bedrock,gauthierm/bedrock,andreadelrio/bedrock,jacshfr/mozilla-bedrock,malena/bedrock,mmmavis/lightbeam-bedrock-website,mahinthjoe/bedrock,sgarrity/bedrock,mozilla/bedrock,l-hedgehog/bedrock,mahinthjoe/bedrock,schalkneethling/bedrock,sylvestre/bedrock,pascalchevrel/bedrock,kyoshino/bedrock,malena/bedrock,yglazko/bedrock,flodolo/bedrock,yglazko/bedrock,mozilla/bedrock,TheJJ100100/bedrock,hoosteeno/bedrock,TheoChevalier/bedrock,mmmavis/lightbeam-bedrock-website,mkmelin/bedrock,malena/bedrock,chirilo/bedrock,pmclanahan/bedrock,mkmelin/bedrock,TheJJ100100/bedrock,pmclanahan/bedrock,kyoshino/bedrock,mahinthjoe/bedrock,mermi/bedrock,andreadelrio/bedrock,ckprice/bedrock,jacshfr/mozilla-bedrock,craigcook/bedrock,yglazko/bedrock,malena/bedrock,rishiloyola/bedrock,kyoshino/bedrock,petabyte/bedrock,jpetto/bedrock,gerv/bedrock,mahinthjoe/bedrock,dudepare/bedrock,CSCI-462-01-2017/bedrock,craigcook/bedrock,analytics-pros/mozilla-bedrock,mmmavis/lightbeam-bedrock-website,ericawright/bedrock,ckprice/bedrock,analytics-pros/mozilla-bedrock,gerv/bedrock,Sancus/bedrock,jgmize/bedrock,CSCI-462-01-2017/bedrock,davehunt/bedrock,alexgibson/bedrock,andreadelrio/bedrock,kyoshino/bedrock,chirilo/bedrock,mozilla/bedrock,pmclanahan/bedrock,davehunt/bedrock,bensternthal/bedrock,sylvestre/bedrock,amjadm61/bedrock,gauthierm/bedrock,jpetto/bedrock,MichaelKohler/bedrock,TheoChevalier/bedrock,petabyte/bedrock,davehunt/bedrock,rishiloyola/bedrock,SujaySKumar/bedrock,pascalchevrel/bedrock,pmclanahan/bedrock,flodolo/bedrock,dudepare/bedrock,l-hedgehog/bedrock,Sancus/bedrock,Sancus/bedrock,schalkneethling/bedrock,SujaySKumar/bedrock,mmmavis/bedrock,jgmize/bedrock,sgarrity/bedrock,yglazko/bedrock,TheoChevalier/bedrock,pascalchevrel/bedrock,schalkneethling/bedrock,ckprice/bedrock,MichaelKohler/bedrock,chirilo/bedrock,craigcook/bedrock,ckprice/bedrock,gerv/bedrock,flodolo/bedrock,sgarrity/bedrock,glogiotatidis/bedrock,mkmelin/bedrock,glogiotatidis/bedrock,sgarrity/bedrock,TheJJ100100/bedrock,Jobava/bedrock,mermi/bedrock,alexgibson/bedrock,amjadm61/bedrock,l-hedgehog/bedrock,jacshfr/mozilla-bedrock,marcoscaceres/bedrock,mmmavis/bedrock,CSCI-462-01-2017/bedrock,Sancus/bedrock,jpetto/bedrock,marcoscaceres/bedrock,gerv/bedrock,jacshfr/mozilla-bedrock,MichaelKohler/bedrock,SujaySKumar/bedrock,hoosteeno/bedrock,petabyte/bedrock,jgmize/bedrock,hoosteeno/bedrock,MichaelKohler/bedrock,mozilla/bedrock,mmmavis/bedrock,ericawright/bedrock,jacshfr/mozilla-bedrock,rishiloyola/bedrock,l-hedgehog/bedrock,alexgibson/bedrock,pascalchevrel/bedrock,analytics-pros/mozilla-bedrock,SujaySKumar/bedrock,flodolo/bedrock,mmmavis/bedrock,sylvestre/bedrock,jpetto/bedrock,chirilo/bedrock,gauthierm/bedrock,ericawright/bedrock,gauthierm/bedrock,amjadm61/bedrock,dudepare/bedrock,Jobava/bedrock,marcoscaceres/bedrock,bensternthal/bedrock,amjadm61/bedrock,amjadm61/bedrock,mkmelin/bedrock,bensternthal/bedrock,jgmize/bedrock,TheJJ100100/bedrock,glogiotatidis/bedrock,craigcook/bedrock,marcoscaceres/bedrock,mermi/bedrock