Add support for REDIS_URL and DATABASE_URL in settings.
Add support for REDIS_URL and DATABASE_URL in settings.

(preparation for Heroku support - #1092)

chriszs/redash,alexanderlz/redash,rockwotj/redash,EverlyWell/redash,44px/redash,stefanseifert/redash,easytaxibr/redash,getredash/redash,ninneko/redash,imsally/redash,crowdworks/redash,imsally/redash,EverlyWell/redash,easytaxibr/redash,44px/redash,denisov-vlad/redash,guaguadev/redash,moritz9/redash,amino-data/redash,hudl/redash,rockwotj/redash,guaguadev/redash,crowdworks/redash,useabode/redash,easytaxibr/redash,denisov-vlad/redash,chriszs/redash,crowdworks/redash,moritz9/redash,amino-data/redash,akariv/redash,getredash/redash,vishesh92/redash,getredash/redash,rockwotj/redash,M32Media/redash,easytaxibr/redash,vishesh92/redash,imsally/redash,alexanderlz/redash,alexanderlz/redash,denisov-vlad/redash,imsally/redash,getredash/redash,EverlyWell/redash,alexanderlz/redash,EverlyWell/redash,getredash/redash,ninneko/redash,44px/redash,stefanseifert/redash,guaguadev/redash,akariv/redash,guaguadev/redash,chriszs/redash,stefanseifert/redash,moritz9/redash,hudl/redash,stefanseifert/redash,44px/redash,stefanseifert/redash,M32Media/redash,ninneko/redash,M32Media/redash,vishesh92/redash,hudl/redash,vishesh92/redash,hudl/redash,useabode/redash,moritz9/redash,akariv/redash,amino-data/redash,crowdworks/redash,akariv/redash,useabode/redash,chriszs/redash,ninneko/redash,rockwotj/redash,easytaxibr/redash,akariv/redash,ninneko/redash,useabode/redash,amino-data/redash,guaguadev/redash,denisov-vlad/redash,denisov-vlad/redash,M32Media/redash