fix fides

[FFroehlich]

fixes mismatch between fval from optimizer and history (fides was pretending it is returning fvals while it was actually returning chi2 values.

[codecov-commenter]

Codecov Report

Merging #741 (a67a54f) into develop (0c88715) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop     #741   +/-   ##
========================================
  Coverage    33.83%   33.83%           
========================================
  Files           99       99           
  Lines         6730     6730           
========================================
  Hits          2277     2277           
  Misses        4453     4453           

Impacted Files	Coverage Δ
pypesto/optimize/optimizer.py	82.60% <ø> (ø)

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