Kotlin API fixes

Fix a number of nullability issues from the Kotlin conversion in the library API for subclassing.

Convert library to Kotlin

Convert the library to kotlin and fix a number of SpannableStringBuilder/Keyboard edge case bugs. Unlike beta01, this probably needs more testing before it's ready for production use.

Migrate to Android X

This should be fine for production use, but I'm expecting to make a few other possibly breaking behavior changes before 4.0.0 RC

Text input mangling and ellipsize crash fixes

• Fix an issue where some text input would be erased if it was similar to the previous search (#381)
• Fix a crash on collapsing with no text in the view (and possibly at other times as well) (#380)

Fix tokenization for threshold of 1

• Fix #379: allow a threshold of 1 to correctly prompt for results on the first letter typed.

Core text re-write

Completely re-wrote the core text handling code to provide a better structure for handling more complex text input.

Fixes: #378, #39, #132, #218, #226, #127, #172, #179, #183, #186, #228, #366, #238, #267.

Clear selections on focus change

• clear selections when the field changes focus
• fix a memory leak in the token click handling code

Respect tokenization style

Correctly supplies raw text data for tokens.

Accessibility improvements

2.0.6

Update version for 2.0.6/12

More empty view fixes

• Prevent enter on empty view with hint from adding a token in some cases
• Don't run filter on hint text when showing drop down on empty view