issue #24 access trr files
close #32: get trr velcoties
cleanup
close #34: different time types
Merge branch 'diff-time-types' into trr-pos-vel-time

* diff-time-types:
  close #34: different time types
Merge branch 'trr-pos-vel-time'

* trr-pos-vel-time:
  close #34: different time types
  cleanup
  close #32: get trr velcoties
  issue #24 access trr files