Add permutecomps/permutecomps!

[dahong67]

New function for permuting the components in a CPD.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 8 lines in your changes missing coverage. Please review.

Project coverage is 97.70%. Comparing base (efae337) to head (72e3091).
Report is 1 commits behind head on master.

Files	Patch %	Lines
src/cpd.jl	0.00%	8 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##            master      #66      +/-   ##
===========================================
- Coverage   100.00%   97.70%   -2.30%     
===========================================
  Files           13       11       -2     
  Lines          369      349      -20     
===========================================
- Hits           369      341      -28     
- Misses           0        8       +8     

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[dahong67]

Not particularly memory-efficient since the slices make copies. Alternatively, could define this in terms of swaps, analogous to: https://github.com/JuliaLang/julia/blob/99d1d6723d72d43074b5d2765e63d08439989e8e/base/combinatorics.jl#L66-L95

That said, good enough for now - merging! Tracking the possible improvement in #6