Force real probabilities to avoid inexact error

[david-pl]

Fixes #335

[david-pl]

We need the fix here SciML/DiffEqBase.jl#769 for builds to pass.

[codecov]

Codecov Report

Merging #337 (3de7b6b) into master (b2618ee) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #337   +/-   ##
=======================================
  Coverage   98.27%   98.27%           
=======================================
  Files          16       16           
  Lines        1335     1335           
=======================================
  Hits         1312     1312           
  Misses         23       23           

Impacted Files	Coverage Δ
src/mcwf.jl	100.00% <100.00%> (ø)

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