Although an HTTP request ending with `.png` could return anything,
this particular source is referring to vector tiles, so an example
with an URL ending in `.pbf` is more appropriated.

Make it clear that text-rotate is not an interpolated property

Fast, semantically aware style diff utility. The differ compares two
stylesheets creating a list of changes. Operations produced by the diff
resemble the mapbox-gl-js API in spirit. Any error creating the diff will
fall back to the 'setStyle' operation.

Operations:
- setStyle
- addLayer
- removeLayer
- setPaintProperty
- setLayoutProperty
- setFilter
- setLayerZoomRange
- setLayerProperty
- addSource
- removeSource
- setConstant
- setSprite
- setGlyphs
- setTransition

Example diff:
    [
        { command: 'setConstant', args: ['@water', '#0000FF'] },
        { command: 'setPaintProperty', args: ['background', 'background-color', 'black'] }
    ]

Applying the diff is an exercise left to each mapbox-gl implementation. A
crude mapbox-gl-js implementation would look like:
    var changes = diff(oldStylesheet, newStylesheet);
    try {
        map.batch(function (batch) {
            changes.forEach(function (change) {
                batch[change.command].apply(batch, change.args);
            });
        });
    } catch (e) {
        console.warn('Unable to apply diff:', e);
        map.setStyle(newStylesheet);
    }

Fix misleading source example

per #324 (comment)

text-rotate is an interpolated property, but like other layout
properties, it is evaluated only at integer zoom levels.

This reverts commit d30b4e8.

Style diff

Remove color ops from v8

#255

This happens in mapbox-gl-styles. Doing it here too creates a circular
dependency.

Conflicts:
	CHANGELOG.md
	package.json

- remove setConstant
- add setCenter
- add setZoom
- add setBearing
- add setPitch

Issue: #338

'pitch' follows 'center', 'zoom' and 'bearing' to define the default
camera position. 0 degrees is perpendicular to the surface.

Issue: #341

In new versions of Node and browserify `URL.parse()` URL encodes
properties on the resulting object. This has the effect of breaking the
migration script in the browser.

We can decodeURI the path segments we need to compare in a manner that is
backwards and future compatible.

Tested with:
- browserify
- Node 0.10
- IO 3.0

Every other layer type already supports visibility.

Types were made more specific to add extra type safety around constants.
Without constants, we no longer need these more specific types. Fewer,
well-known types makes tooling support easier.

- '*-enum' -> 'enum'
- '*-array' -> 'array'
- 'opacity' -> 'number'
- 'field-template' -> 'string'

Issue: #340