saga: 2.1.0 - Renamed Formula

Renamed formula to saga-gis
Reverted changes to saga-core
Removed saga alias, since there are now two formulas that start with
saga

saga 2.1.0 - Added saga-gis.rb

For some reason the saga-gis.rb file is missing. This should fix that.

saga: 2.1.0 - Renamed Formula

Renamed formula to saga-gis
Reverted changes to saga-core
Removed saga alias, since there are now two formulas that start with
saga