Fix optional import

[devmotion]

Currently, loading both Soss and SampleChainsDynamicHMC does not work correctly:

julia>] add Soss, SampleChainsDynamicHMC
julia> using Soss, SampleChainsDynamicHMC
┌ Warning: Package Soss does not have SampleChainsDynamicHMC in its dependencies:
│ 
│   •  If you have Soss checked out for development and have added SampleChainsDynamicHMC as a
│      dependency but haven't updated your primary environment's manifest file, try Pkg.resolve().
│ 
│   •  Otherwise you may need to report an issue with Soss
│ 
│ Loading SampleChainsDynamicHMC into Soss from project dependency, future warnings for Soss are
└ suppressed.

The optional import of SampleChainsDynamicHMC is not correct: As stated in the documentation of Requires,

In the @require block, or any included files, you can use or import the package, but note that you must use the syntax using .Gadfly or import .Gadfly, rather than the usual syntax. Otherwise you will get a warning about Gadfly not being in dependencies.

Unfortunately, AFAIK it is not possible to detect this error when running the tests if the optional dependency is a test dependency.

[codecov[bot]]

Codecov Report

Merging #256 (7eb87fe) into master (0440210) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #256   +/-   ##
=======================================
  Coverage   24.91%   24.91%           
=======================================
  Files          49       49           
  Lines        1204     1204           
=======================================
  Hits          300      300           
  Misses        904      904           

Impacted Files	Coverage Δ
src/samplechains/dynamichmc.jl	0.00% <ø> (ø)

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[cscherrer]

Great! Thank you @devmotion

[devmotion]

Is it possible to release a new version with the fix? I already updated the version number in this PR.

[cscherrer]

Thanks for the reminder, in progress now

[devmotion]

Great, thanks!