More UserStory functionality

[lucasreed]

adding functionality to assign a user to a story; also functionality for getting URLs to entities

[codecov]

Codecov Report

Merging #26 (50caaf5) into master (aed8570) will decrease coverage by 0.40%.
The diff coverage is 5.26%.

@@            Coverage Diff             @@
##           master      #26      +/-   ##
==========================================
- Coverage   20.72%   20.32%   -0.41%     
==========================================
  Files          12       13       +1     
  Lines         357      369      +12     
==========================================
+ Hits           74       75       +1     
- Misses        271      282      +11     
  Partials       12       12              

Impacted Files	Coverage Δ
general.go	0.00% <0.00%> (ø)
userstory.go	0.00% <0.00%> (ø)
client.go	58.06% <100.00%> (+0.45%)	⬆️

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