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
Do not scale above minzoom and maxzoom in touch zoom action
Fixing line too long error
adding alt tag to marker icons
Changed main module file to use un-minified version.

This makes the debugging process easier and also makes it possible to choose your own minifier when using browserify or similar bundlers.
Remove leftover code from the draggable/tap cleanup. Fixes #2103
Merge pull request #2111 from danzel/fix-2103

Remove leftover code from the draggable/tap cleanup. Fixes #2103
Merge pull request #2112 from jimmytidey/master

adding alt tag to marker icons
Merge pull request #2109 from icetan/patch-1

Changed main module file to use un-minified version.
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
Merge pull request #2117 from danzel/fix-2094

Fix click events when touch zooming on ie 10
Allow double quotes in template strings fixes #2120
Make Mocha ignore leaks properly and do some space -> tab replacement
Adding bounceAtZoomLimits option
Fixing long line
Merge pull request #2072 from trevorpowell/master

Don't bounce near zoom limits on touch zoom
update dependencies