begin updating .osx for Yosemite

- commented out the -currentHost defaults commands for trackpad behavior since it wasn't working for me

- the new cmd+return Mail shortcut is also a fix for Mavericks (see #381)
I forget if I thought it was necessary (yeah it's not) but I probably removed it when I removed `-string` from the ⌘ + return line for Mail.app (which was necessary).