[WIP] Changes holetraj start/stop/step keywords (Issue #2513)

[IAlibay]

Fixes #2513
Towards #2443

Changes made in this Pull Request:

• Removes support for start/stop/step in :meth:HOLEtraj.__init__.
• Adds a check_slice_indices to the values passed to :meth:HOLEtraj.run.

PR Checklist

• Tests? (Don't have HOLE on my machine, relying on Travis in this instance)
• Docs?
• CHANGELOG updated?
• Issue raised/referenced?

[codecov]

Codecov Report

Merging #2514 into develop will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop    #2514   +/-   ##
========================================
  Coverage    90.49%   90.49%           
========================================
  Files          170      170           
  Lines        23355    23355           
  Branches      3077     3077           
========================================
  Hits         21136    21136           
  Misses        1623     1623           
  Partials       596      596

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update fcf8e23...0067e92. Read the comment docs.

[orbeckst]

Looks pretty good , thank you. There's an issue with kwargs, which needs to be documented (versionchanged and CHANGELOG) and fixed.

Please also add CHANGELOG entry.