'Enter' on configuration authentication

[conspacer]

I have been using this plugin quite a bit. Its quite handy, thank you. If you plan to keep developing it, here is a small nag feature suggestion: On authenticating to open the servers list, currently you must use the mouse to click 'OK'. Adding a keyboard 'Enter' for those of us keyboard junkies would be helpful.

[Tugzrida]

@conspacer I fixed this in #84 but it doesn't look like @kooohei has re-uploaded the extension to the brackets registry. If you install the extension from the zip of the repo (https://github.com/kooohei/brackets-synapse/archive/master.zip) then that should work.