0.13.0-rc.2

• [Fix] Prometheus backend wasn't working correctly for non-taged render requests (#465, thx to @menai34 for proposed fix)
• [Fix] Fix panic when using prometheus tagged response for non-tagged queries in groupByTags function (and maybe more)
• [Fix] Add proper aliases for aggregate functions - that would make groupByTags properly usable with functions like diff and total.