Autocomplete

This will add autocomplete for issues, users and emojis to the issue add and edit view.

### Emojis
![debug-3903](https://cloud.githubusercontent.com/assets/33978/4694164/2c6e5b4e-57bf-11e4-84c7-eb0330aa29b7.png)

### Issues
![debug-3904](https://cloud.githubusercontent.com/assets/33978/4694165/308fb3e4-57bf-11e4-9df1-ba4ef5fba289.png)

### Users
![debug-3905](https://cloud.githubusercontent.com/assets/33978/4694166/33c4c630-57bf-11e4-9ff1-e685868b6bfc.png)

As seen on GitHub :wink: 
It will search users in the tracker's DB. So if someone having GH account did not login to tracker then you will not find him. I do not think that it is critical? ;)