Updated to Vim 7.4

It appears that this installer now writes to the 64-bit registry, so the ps code checking the architecture is not longer necessary. Note that `cinst vim` must be run from 64-bit cmd or 64-bit powershell for it to work correctly.

Also, despite passing /S, this installer is still a bit noisy. Shows two Y/N dialogs during the install. I couldn't find a way to disable those.

Tested on 64-bit Windows 7.