Use QuantEcon.next_k_array! in support_enumeration

[monsij]

Closes Issue #70

I have replaced all instances of _next_k_array! with next_k_array! and _next_k_combination with k_array_rank .Both from QuantEcon.jl

[codecov-io]

Codecov Report

Merging #80 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master      #80   +/-   ##
=======================================
  Coverage   96.36%   96.36%           
=======================================
  Files           6        6           
  Lines         468      468           
=======================================
  Hits          451      451           
  Misses         17       17

Impacted Files	Coverage Δ
src/support_enumeration.jl	98.85% <100%> (ø)	⬆️

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[monsij]

Kindly review @oyamad

[oyamad]

@monsij Thanks, but it is not what is meant in #70 (sorry for my poor explanation!).

Maybe it will be easier to see what the task really is by looking at the corresponding change QuantEcon/QuantEcon.py@a215f1f in the Python version. Could you take some time to look at that commit?

[monsij]

I'll get back to it once I understand it.Thanks @oyamad

[monsij]

I am closing the pull request as the changes made are wrong.