Correct build version

Add hiding and showing of modifier keys

Library:

Fix crash when unsetting key background (by setting it to 0).
Allow setting the layout for the keyboard view itself in xml as attribute "layout".
Add getters for keyboard and popupwindow instances to NumberKeyboardPopup

Sample:
Update sample to include AOSP style keyboard via "layout" attribute.

Fix layout issues when using dynamic height davidmigloz#10

Use Autosizing TextViews davidmigloz#8

Update README.md

Update dependencies to 26 davidmigloz#2

Library crashes when running on API 19 davidmigloz#1

Initial version