Remove extent property from ol.tilegrid.TileGridOptions

This follows tilegrid extent_ property removal from #216.
Merge pull request #237 from bbinet/tilegrid_extent_cleanup

Remove extent property from ol.tilegrid.TileGridOptions
Remove css size dependent rule (hover color)
Refactor projection architecture
Cope with axis orientation for tiled WMS sources
Cope with axis orientation in single image WMS sources
Add EPSG:4326 example
Set ol-zoom content in css using :before pseudo class
Only require things that start with a capital letter
Separate ol.projection module from ol.Projection class
Make Proj4js classes and functions private
Merge pull request #244 from fredj/zoom-control

Zoom control
Add hyperbolic functions
Add ol.tilegrid.XYZ tests
SIMPLE and WHITESPACE builds
Prefer the canvas renderer over dom.
Merge pull request #248 from bbinet/prefer-canvas

Prefer the canvas renderer over dom.
Merge pull request #245 from twpayne/projection-refactoring

Projection refactoring
Merge pull request #246 from twpayne/xyztilegrid-tests

Add ol.tilegrid.XYZ tests
Merge pull request #247 from twpayne/hyperbolic-functions

Add hyperbolic functions