Support input method

[tangxinfa]

The node can only input english, can't switch to other input method.

I run labyrinth 0.6 on archlinux with fcitx input method tool.

[takluyver]

See also #2. I don't know much anything about input methods, so I'm not going to fix this, but if you can make a PR and satisfy me that it works and isn't going to break things, I'll be happy to merge it.