Don't fail when no featues are found in ol.format.TopoJSON
Use projection option instead of reprojectTo

The projection option for vector file sources currently has no good meaning.  The reprojectTo option is used to set the projection for cached features.  This change makes it so the projection option is used for this purpose.  The getProjection method (not currently exported) can then be used to get the cached feature projection.

This also removes the default of 'EPSG:3857' for vector file sources.  If a projection is not configured, features will not be transformed.
Make ol.Map#isDef checking stricter
Assert that pixel is non-null when positioning overlay
Merge pull request #1609 from twpayne/stricter-map-defined

Stricter map defined
Merge pull request #1633 from twpayne/no-fail-in-topojson

Don't fail when no featues are found in ol.format.TopoJSON
Fix typo in text rendering
Use evt.coordinate instead of evt.getCoordinate()
Merge pull request #1636 from twpayne/fix-text-bug

Fix typo in text rendering
Merge pull request #1637 from fredj/getfeatureinfo-example

Use evt.coordinate instead of evt.getCoordinate()
Add a keyboardEventTarget option to the map

This option allows specifying the element to listen to keyboard events on.
Accept string for keyboardEventTarget option
Change keyboardEventTarget doc as requested by @probins
Merge pull request #1145 from elemoine/keyboard

Add a keyboardEventTarget option to the map
Close the polygon created by ol.render.Box
Simplify code in ol.render.Box#createGeometry_
Fix typo in tests
Fix closing tag in tests
Add ol.xml.load
Use ol.xml.load in ol.format.XML