Update old namespace link and incorrect UI link

[aaronranard]

Issue:
I noticed the npm link command is out of date in the contribution guide and updated it to what I believe it should be, as well as a link to the Storybook UI page.

What I did

Went through the process of linking the storybook source code locally based on the contribution guide and fixed the out of date docs

How to test

[shilman]

Thanks! LGTM!

[shilman]

@orta Travis build is failing due to DANGER_GITHUB_API_TOKEN environment variable being stripped for PR's issued from forked repos:

Encrypted environment variables have been removed for security reasons.
See https://docs.travis-ci.com/user/pull-requests/#Pull-Requests-and-Security-Restrictions

Have you ever seen this, and do you have a workaround?

[codecov]

Codecov Report

Merging #1271 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1271   +/-   ##
=======================================
  Coverage   13.73%   13.73%           
=======================================
  Files         207      207           
  Lines        4638     4638           
  Branches      519      574   +55     
=======================================
  Hits          637      637           
+ Misses       3552     3510   -42     
- Partials      449      491   +42

Impacted Files	Coverage Δ
addons/knobs/src/components/PropField.js	10.86% <0%> (ø)	⬆️
app/react/src/client/preview/error_display.js	0% <0%> (ø)	⬆️
app/react/src/server/babel_config.js	44.82% <0%> (ø)	⬆️
addons/info/src/components/Props.js	0% <0%> (ø)	⬆️
addons/knobs/src/components/types/Boolean.js	11.62% <0%> (ø)	⬆️
lib/ui/src/modules/ui/configs/init_panels.js	25% <0%> (ø)	⬆️
addons/knobs/src/KnobStore.js	6.81% <0%> (ø)	⬆️
addons/info/src/components/PropTable.js	0% <0%> (ø)	⬆️
app/react-native/src/bin/storybook-start.js	0% <0%> (ø)	⬆️
lib/ui/src/modules/api/actions/api.js	49.42% <0%> (ø)	⬆️
... and 25 more

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