`vim`: just after `:!some_command` has finished running, touch gestures send arrow keys again

## Summary
* When `vim` prints `Press ENTER or type command to continue`, touch gestures stop sending scroll gestures and start sending arrow keys.
* This is because `vim` switches back to the alternate screen just after the command finishes running -- when it prints `Press ENTER or type command to continue`.
* This makes scrolling difficult when running a command like this in `vim`.
* **For me, at least, this isn't a big issue** (see workarounds).

## Existing Workarounds
* Select text when `vim` prints `Press ENTER or type command to continue`. This enables hterm scrolling.
* Send command output to a `vim` buffer: `:tabe | %!command_here`.
* Doesn't work for commands that need input.

## Potential fixes
* When `vim` is running, if the last line of output reads `Press ENTER or type command to continue`, vertical swipes could switch back to scrolling (from arrow keys).
* If the user isn't scrolled completely to the end of the output, make touch gestures only scroll. (Should be easy to implement, but not a complete fix).
* When running `vim`, making two-finger vertical swipes scroll `hterm`. (Also not a complete fix).
* Adding a gesture that toggles whether vertical gestures scroll or send arrow keys.
* This would be a (potentially) less intuitive UI...
* Is there a way to make `vim` switch back to its alternate screen after the user presses `ENTER or types a command?