Deleting first letter of a mention moves cursor to the end of the input

[bbmreed]

To reproduce:

• using the demo: http://effektif.github.io/react-mentions/
• In the first input, the text (currently) reads:

Hi John Doe, 

let's add joe@smoe.com and John Doe to this conversation... 

• Delete the first J in Hi John Doe
• cursor jumps to the end of the input

Gif showing behavior:

https://gyazo.com/ef903339a6d587da988f25c26c361467