Doesn't work with Mail 11

[flowerornament]

Temporary fix, thanks to @jhollington and @wunc in #43:

1. Run the find_uuid.sh script in the project root in Terminal, which should output the new Mail UUID.
2. Edit the info.plist file and add a new Supported10.13PluginCompatibilityUUIDs key list.
3. Add the new UUID to the list.

Probably overkill, but my info.plist looks like this now:

<string>GMailinator</string>
<key>Supported10.12PluginCompatibilityUUIDs</key>
<array>
  <string>[old-uuid]</string>
  ...
  <string>[new-uuid]</string>
</array>
<key>Supported10.13PluginCompatibilityUUIDs</key>
<array>
  <string>[old-uuid</string>
  ...
  <string>[new-uuid]</string>
</array>
<key>SupportedPluginCompatibilityUUIDs</key>