Make zoom control animation duration configurable
Make double click zoom animation duration configurable
Make keyboard zoom animation duration configurable
Add support for ol.overlay center positioning
Update overlay example with center positioning
Update ol.overlay exports for center positioning
Always provide lib functions, conditionally provide scope
Avoiding unhandled errors

These tests were generating errors that were not caught because they were outside the `it` functions.
Merge pull request #1102 from tschaub/expr-lib

Always use ol.expr.lib when calling evaluateFeature.
Fix overlay positioning in geolocation example
Fix overlay positioning in icon example
Merge pull request #1101 from bbinet/overlay_center_positioning

ol.overlay center positioning
Add stroke properties to text symbolizer literal
Add stroke support for text symbolizers
Minor apidoc updates
Merge pull request #1103 from fredj/doc

Minor apidoc updates
Make mouse wheel zoom animation duration configurable
Make touch zoom animation duration configurable
Add zoomDuration option to interaction defaults
Only install animations if duration > 0