Hey
I just tried that to solve my install issue but I get the following on $ionic lib update:
Arthur:ionFullApp_1.3.0 arnaud$ ionic lib update --allow-root/usr/local/lib/node_modules/bower/node_modules/configstore/index.js:56
throw err;
^
Error: EACCES: permission denied, open '/Users/arnaud/.config/configstore/bower-github.yml'
You don't have access to this file.
at Error (native)
at Object.fs.openSync (evalmachine.<anonymous>:549:18)
at Object.fs.readFileSync (evalmachine.<anonymous>:397:15)
at Object.create.all.get (/usr/local/lib/node_modules/bower/node_modules/configstore/index.js:34:29)
at Object.Configstore (/usr/local/lib/node_modules/bower/node_modules/configstore/index.js:27:44)
at readCachedConfig (/usr/local/lib/node_modules/bower/lib/config.js:19:23)
at defaultConfig (/usr/local/lib/node_modules/bower/lib/config.js:11:12)
at Object.<anonymous> (/usr/local/lib/node_modules/bower/lib/index.js:40:32)
at Module._compile (module.js:435:26)
at Object.Module._extensions..js (module.js:442:10)`I went to the mentioned directory and I could not find the file 'bower-github.yml'
Therefore I cannot install sass. 
Any help is appreciated.