* Convert tests in `demo-playground`

* Convert tests in `flexbox`

When configration changes are handled manually, onSaveInstanceState
wasn't called in the FlexboxLayoutManager. Thus flex lines previously
calculated with the prior configuration including width of the screen
were not discarded.

This PR introduces the fields of the width/height of the previous
measurement. If the width (or height depending of the flex direction) is
different from the previous value discard the prior flex lines.

This PR also fixes the cases where width is getting changed in the multi
window mode.

Change-Id: I6bdf29d1682cf15c26776f6ffcce87fd3b7f4ef6

Change-Id: Ibad62661879d547c16c30477947f8f1acf808095

- Adds gradle setting files for bintray and maven
- rename the module name from 'library' to 'flexbox' to match the artifactId

Change-Id: I292d99329c4d44b0e609e90ad88f1373f56e2187

Change-Id: I928dc49ca3f0f21e7077eb96e1f0360dd0dfde31