* Add support for the fish shell
Fixes#1142
The fish shell is not POSIX-compliant. As a result, the installation
command's use of `&&` caused `updatePlugins` to fail, erroneously
claiming there would be details in `~/.hyper_plugins/npm-debug.log`.
They of course weren't there because the command it tried to run was an
invalid command. I've added an object to choose the install command to
run based on the shell you're in, and a very basic test to determine if
we're in fish. Most shells should be able to be handled by the
'default' key, so for now it just checks to see if it's fish by doing a
regex on the configured `shell` option.
* Rename default -> posix
993b8f6833