Mobile Tracker now integrated with GMap API 3

Closes #2

* updated build.sh
* lowered the size of target*.png to 30x30 px
* removed a lot of legacy code
* optimized a lot of the routines
* implement follow functionality, which replaces pan on expand
* map is more responsive and snappy across devices

* fixes dragging issue on android devices; Closes #4
* horizon range drawing is handled by google api, which will
  properly visualize it over the projection; Closes #11
* enabled zoom slider; Closes #13