Fix polynomial power overflow bug

[Lasagnenator]

Fixes #487.

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (a140a46) 96.33% compared to head (d8bb893) 96.33%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #488   +/-   ##
=======================================
  Coverage   96.33%   96.33%           
=======================================
  Files          46       46           
  Lines        5842     5842           
=======================================
  Hits         5628     5628           
  Misses        214      214           

Impacted Files	Coverage Δ
src/galois/_polys/_dense.py	96.45% <100.00%> (ø)

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[Lasagnenator]

I wasn't sure which branch you wanted to merge into so I just put master (the default).

[mhostetter]

Thanks!

Can you select release/0.3.x (should be able to change in the GitHub webpage)? I'll merge this there and then release this bug fix in v0.3.6.