Configurable table view content insets

Add possibility to configure table view content insets in MBTableViewPageController when keyboard is present.

Insert items to sections

0.4.0

Update travis yml

Disabling custom cell separators

Added possibility to disable custom cell separators to use standard UITableView cell separators instead.

Nullability annotations

0.2.1

Bump version to 0.2.1

Add support for switch cells

Added support for switch cells (thanks to Johannes)

Fixed bugs

Fix the issue with the text field frame calculation.

Improve support for long forms on small displays.

Automatically update table view's content offset when keyboard appears/hides.