Controller.js Cache this instead of using Fn#bind

improves readability and it's smaller when minified
Add $on --an addEventListener wrapper
Code cleanup

app.js: DRY functions
store.js: toss unneeded var, return/break early in store#find &
store#save
store.js & model.js: optional id argument in Store#save is last
store.js & view.js: item IDs are never stings anymore