Fix #172: respect the `shiny.launch.browser`option

[danschrage]

See #172: If the user sets the shiny.launch.browser option to FALSE when running shinystan outside of RStudio, this change ensures that launch_shinystan() respects that. Otherwise, the default behavior (launch.browser=TRUE) is preserved.

[codecov-io]

Codecov Report

Merging #173 into master will decrease coverage by 4.26%. The diff coverage is 0%.

@@            Coverage Diff             @@
##           master     #173      +/-   ##
==========================================
- Coverage   97.09%   92.83%   -4.27%     
==========================================
  Files          10       10              
  Lines         896      795     -101     
==========================================
- Hits          870      738     -132     
- Misses         26       57      +31

Impacted Files	Coverage Δ
R/launch_shinystan.R	35% <0%> (-3.1%)	:arrow_down:
R/misc.R	80% <0%> (-20%)	:arrow_down:
R/rhat_ess_monitor_fns.R	94.2% <0%> (-5.8%)	:arrow_down:
R/shinystan-objects.R	93.12% <0%> (-5.73%)	:arrow_down:
R/update_sso.R	93.54% <0%> (-3.83%)	:arrow_down:
R/generate_quantity.R	97.22% <0%> (-2.78%)	:arrow_down:
R/retrieve.R	97.33% <0%> (-1.37%)	:arrow_down:
R/sso-metadata.R	100% <0%> (ø)	:arrow_up:
R/drop_parameters.R	100% <0%> (ø)	:arrow_up:
... and 1 more

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[jgabry]

@VeenDuco added this fix to the branch with the alpha version but I just noticed that we didn't merge this into master. i think we should include this fix in the current version on master too so merging now.