Fix Dihedral box

[ALescoulie]

I added a box argument to calc_dihedrals similar to what is present in MDAnalysis

[codecov]

Codecov Report

Merging #198 (a191e82) into develop (5628473) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff            @@
##           develop     #198   +/-   ##
========================================
  Coverage    78.53%   78.53%           
========================================
  Files           11       11           
  Lines         1677     1677           
  Branches       250      250           
========================================
  Hits          1317     1317           
  Misses         276      276           
  Partials        84       84           

Impacted Files	Coverage Δ
mdpow/analysis/dihedral.py	100.00% <100.00%> (ø)

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[orbeckst]

I am going to approve without asking for the obligatory "could you please test this" because I know that it's tested in MDA — that's why using existing (trustworthy) libraries is good!

[orbeckst]

I think you need to update your own branch because lot's of old commits are showing up. The squash merge just dealt with it but in the future it would be good to have clean PRs for review.