Quad gpu fix

[zsteve]

This PR fixes type issues that prevent quadreg from running with CuArrays, and adds a test for that setting. Also fixes a bug with the Armijo step search which I found for certain inputs caused the solver to get stuck.

[coveralls]

Pull Request Test Coverage Report for Build 1176317897

• 12 of 12 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.02%) to 97.671%

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Totals
Change from base Build 1174249145:	0.02%
Covered Lines:	671
Relevant Lines:	687

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💛 - Coveralls

[codecov-commenter]

Codecov Report

Merging #121 (22b4f92) into master (d33f1cf) will increase coverage by 0.01%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #121      +/-   ##
==========================================
+ Coverage   97.65%   97.67%   +0.01%     
==========================================
  Files          13       13              
  Lines         682      687       +5     
==========================================
+ Hits          666      671       +5     
  Misses         16       16              

Impacted Files	Coverage Δ
src/quadratic_newton.jl	98.16% <100.00%> (+0.08%)	:arrow_up:

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