defaults for min/max Zoom in TileLayer

When overwriting TileLayer options from TileJSON the defaults of
min/max Zoom gets overwritten with `undefined` when not set in
TileJSON which causes the map to break.
Merge pull request #732 from ubergesundheit/minmaxzoom-tilelayer

Set defaults for min/max Zoom in L.mapbox.tileLayer
Remove map.feautureLayer re-use antipattern
Fix markers as links example
updates bower.json version to 1.6.2
Merge pull request #735 from chollier/mb-pages

Updates bower.json version to 1.6.2
Reduce amount of tile host sharding

In fact, only the first URL is ever used internally,
so while here, remove the unused logic from url.base.
Use released leaflet-hash
Use released json3 (v3.3.1)
Don't rely on embed property in tilejson (fixes #728)
Fix incomplete variable rename
Make fancier logged in / logged out guidance.
Trigger signup with js until a better solution exists. Red mapbox/www.mapbox.com#3892
Trigger signup with js until a better solution exists. Ref mapbox/www.mapbox.com#3892
Merge branch 'mb-pages' of github.com:mapbox/mapbox.js into mb-pages
Add latlng case
Update 0100-01-01-map-center-geocoding.html
Updated docs/_layouts/default.html
Update leaflet omnivore version
Update and add leaflet-omnivore examples