add {r} format to url, which returns @2x when retina detected and enabled
fix retina condition
Make options object prototype-inherited

Fixes #2294
Use L.Util.create for class extension
use lighter extend in setOptions, simplify extend
Merge pull request #2300 from Leaflet/prototypal-options

Make options object prototype-inherited
Merge pull request #2304 from jacobtoye/master

Adding Leaflet logo in svg format
made the logo pretty-printed for consistency
Do not ignore custom build parameters

Regression from 941b20671456c6db98414519fb30baee81ea4bfa ("improve size
reporting when building and add gzipped size").
Merge pull request #2306 from Lekensteyn/fix-jake

Do not ignore custom build parameters
make instantiation faster by avoiding callInitHooks where not needed
replace L.Mixin.Events with L.Evented class (bw-compat)
make Evented longer names aliases instead of on/off
replace Events mixin with Evented inheritance
Merge pull request #2296 from urbaniak/retina-tile-url

add {r} format to url, which returns @2x when retina detected and enabled
no parseFloat in LatLng, faster factory (massive speedup)

see http://jsperf.com/leaflet-parsefloat-in-latlng
Merge pull request #2310 from Leaflet/evented

Evented base class to use in favor of mixing in event methods
clean up Class.js
fast event propagation (10x FeatureGroup layer add speedup)
remove DomUtil.getViewportOffset as unnecessary