Input customization point

[viktorasl]

Originated from #53.

As far as I can see there is no trivial way to do this, so I went the easiest way and forced developers implementing listeners to be cautious and do be aware about might-be-clashing manipulations of text and/or attributes.

7e39198 tinily improved removing of autocompleted text leaving preceding character (which is probably a space AFAIK). (e.g "Hello @SD10" becomes "Hello " instead of "Hello")

[rnystrom]

I'm actually reverting this b/c I didn't really think about the long term effects of adding a breaking change w/out a plan for #53.

[viktorasl]

What are the next steps? Is the solution to this should not introduce any breaking changes?

[rnystrom]

@viktorasl breaking changes are fine since this lib is so young, but I think we need to know why this change is required in the long run

_{Sent with GitHawk}

[viktorasl]

My plan is that this implementation will allow manipulating text that will be changed by conforming to MessageTextViewListener protocol. Similarly to the way MessageAutocompleteController is done.

IMHO that's pretty convenient way to tackle this.