Iconify 2.X.X introduces breaking changes, here's the full list:
In build file
compile 'com.joanzapata.android:android-iconify:1.X.X'->compile 'com.joanzapata.iconify:android-iconify-fontawesome:2.X.X'
In layouts
android.widget.IconButton->com.joanzapata.iconify.widget.IconButtonandroid.widget.IconTextView->com.joanzapata.iconify.widget.IconTextViewandroid.widget.IconToggleButton->com.joanzapata.iconify.widget.IconToggleButton
In code
com.joanzapata.android.iconify...->com.joanzapata.iconify...Iconify.IconValue.fa_something->FontAwesomeIcons.fa_something- Nothing in
Applicationclass ->Iconify.with(new FontAwesomeModule())