Unexpected behaivor on Russian keyboard layout

[In your code](https://github.com/developit/tags-input/blob/master/src/tags-input.js#L7) you use key codes to determine which key was pressed. But on Russian keyboard layout we have letter `б` on 188th key code. For example, if I type `яблоко` which means `apple` in english, I get this result:



Start by reading src/tags-input.js at line 7 and reproduce the issue while typing яблоко with a Russian keyboard layout. Compare the key handling for the reported 188 key code with normal text entry; done means Russian letters can be entered without triggering incorrect tag behavior.

索引モデルが issue の本文から書いたものです。