Revert to most of master's logic for SQRLInstallerSpec
Revert to most of master's logic for SQRLInstallerSpec

EdZava/Squirrel.Mac,EdZava/Squirrel.Mac,Squirrel/Squirrel.Mac,emiscience/Squirrel.Mac,Squirrel/Squirrel.Mac,emiscience/Squirrel.Mac,Squirrel/Squirrel.Mac,emiscience/Squirrel.Mac,EdZava/Squirrel.Mac