let's call the app what the user called it

My main reason to fork was that I'm using slate to switch apps and wasn't able to switch to a Chrome SSB. I then found out that the app (eg mine was called "Googlemail") was called "Googlemail" in OS X's app switcher, but in the Activity Monitor, the process was called "Google Chrome". Slate had only access to the process name to switch to the app, so I could only switch to "Google Chrome" but not to "Googlemail" which gets confusing when you've got both apps running simultaneously. With my last commit, the app now is called "Googlemail" and can be referenced by slate.

Furthermore, I sped up the retrieval of Google Chrome and avoided reconverting existing icns files.