v4.1.1

Optimization v4.1.1

Diff since v4.1.0

Merged pull requests:

• Fix typo (#878) (@dreivmeister)
• Check more retcodes from NLopt (#879) (@sumiya11)
• Bump version (#880) (@sumiya11)

Closed issues:

• Incorrect return value classification of FTOL_REACHED from NLopt (#862)
• Running optimizations with maps as input (#875)