LeafletPlayback refactoring

## Source changes

* Removed all dependencies except Leaflet and jQuery;
* Split initialization an data loading routines;
* Renamed `Tick` to `TrackController` and `TickPoint` to `Track`;
* Pass option `marker` to MovableMarker and `layer` to TracksLayer as object or function;
* Added `maxInterpolationTime` option;
* Use marker and path options from geoJSON feature;
* Refactored controls (original control moved to examples/example_2_control.js);

### Files/folders

* Updated README;
* Cleared unnecessary files and folders except `data` and `demo` (otherwise pull-request is too large for GitHub);
* Created examples folder;
* Added Grunt Uglify task;
* Removed Grunt concat with deps;