Movement issue39 update flux function interfaces

[KathrinTessella]

Updated the tests and documentation accordingly. Perhaps we want a better description for the 'Arguments' in the documentation?

[KathrinTessella]

@nick: any suggestion how to improve the argument lists in the documentation? Perhaps that could be done together with issue #52 ?

[goldingn]

Yup, I think that's a good idea - a few words to describe the role of each parameter

[codecov-io]

Current coverage is 69.89%

Merging #56 into master will increase coverage by +0.39% as of b8ee14e

@@            master     #56   diff @@
======================================
  Files            1       1       
  Stmts          469     475     +6
  Branches         0       0       
  Methods          0       0       
======================================
+ Hit            326     332     +6
  Partial          0       0       
  Missed         143     143       

Review entire Coverage Diff as of b8ee14e

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