Add solvers for quadratic interval equations

[codecov-io]

Codecov Report

Merging #68 into master will increase coverage by 3.4%. The diff coverage is 96.29%.

@@           Coverage Diff            @@
##           master     #68     +/-   ##
========================================
+ Coverage    48.3%   51.7%   +3.4%     
========================================
  Files           9      10      +1     
  Lines         354     381     +27     
========================================
+ Hits          171     197     +26     
- Misses        183     184      +1

Impacted Files	Coverage Δ
src/IntervalRootFinding.jl	2.04% <ø> (ø)	:arrow_up:
src/quadratic.jl	96.29% <96.29%> (ø)

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[eeshan9815]

ping @dpsanders

[eeshan9815]

ping @dpsanders

[dpsanders]

Thanks!