Fix on README.md: goals, tested systems, and details
erltrek.hrl: ERLTREK_VERSION is now 0.1
erltrek.erl: add typespec
erltrek_calc: remove unnecessary functions and add typespec

* Remove track_course/4, list_track/4
* Add typespec to galaxy/1
* Fix galaxy/1 return value to the integer coordinates
  (#quadxy{} and #sectxy{} does not allow non-integer values)