Adds support for altitude and 3D GeoJSON

This commit adds a third parameter to the L.LatLon class for specifying
altitude. This is in turn stored in the `.latitude` property for the LatLng
instance. Latitude property will only be set if the latitude parameter is not
undefined, this is done in order to ensure backwards compability.

```javascript
var latlng = new L.LatLng(10, 20, 30);
console.log(latlng.altitude); // prints '30' to the console
```

Similar functionality has been added to L.GeoJSON coordsToLatLng() and
latLngToCoords() methods in order to handle import and export of 3D GeoJSON.

```javascript
var geoJSON = {
  type: 'Feature'
  ,properties: {}
  ,geometry: {
    type: 'Point'
    ,coordinates: [20, 10, 30]
  }
}
var layer = new L.GeoJSON();
layer.addData(geoJSON);
console.log(layer.getLayers()[0].getLatLng().altitude);
```

`NB` It is important to notice that no logic has been added in order to prevent
latitude and longitude to change without appropirate change in altitude – this
must be handled by the application.
Renames L.LatLng property .altitude to .alt
Added getBounds function to CRS
Use CRS's bounds to calculate wrap
panInsideBounds: fit or center, pass options, remove boundsMinZoom

Deltas are calculated on x, y pixel coordinates separately.
Options are propagated from setMaxBounds to panBy.
No panBy loops. Fixes #1908.
test Map#setMaxBounds and Map#panInsideBounds
Allow double quotes in template strings fixes #2120
Make Mocha ignore leaks properly and do some space -> tab replacement
update dependencies
Merge branch 'master' of https://github.com/Leaflet/Leaflet

* 'master' of https://github.com/Leaflet/Leaflet:
  Fixing long line
  Adding bounceAtZoomLimits option
  The drag click avoid hack is needed for touch zooms on ie10 also, when releasing your fingers after a touch zoom click events are generated. Fixes #2094
  Remove leftover code from the draggable/tap cleanup. Fixes #2103
  Changed main module file to use un-minified version.
  adding alt tag to marker icons
  Fixing line too long error
  Do not scale above minzoom and maxzoom in touch zoom action
update changelog [skip ci]
Make Mocha ingore leaks, spaces -> tabs
Whitespace OCD
Hack fix for firefox android layers control. refs #2033
Test pages for rtl support.
Delete ltr/rtl code as its not needed any more, wtf?
Re-add ltr/rtl detection and make getMousePosition work correctly with rtl again when scrolled.
Merge pull request #2121 from jieter/util-template

Allow double quotes in template strings
Add tileloadstart event with tile data
Fix build error, reference layer correctly.