Remove superagent and add got user-agent

[tusbar]

Rewrite all udata related API calls to use got.

Do not merge until sindresorhus/got#622 is released (or don’t forget to update to a version of got that includes that patch before we release this).

This also creates custom got instances that set the User-Agent headers.

There are 2 clients: lib/got.js and plugins/publish-to-udata/got.js with different user agents.

Close #19

[codecov-io]

Codecov Report

Merging #3 into master will increase coverage by 0.01%.
The diff coverage is 0%.

@@            Coverage Diff            @@
##           master      #3      +/-   ##
=========================================
+ Coverage    6.05%   6.07%   +0.01%     
=========================================
  Files          96      98       +2     
  Lines        2164    2157       -7     
=========================================
  Hits          131     131              
+ Misses       2033    2026       -7

Impacted Files	Coverage Δ
plugins/publish-to-udata/app.js	0% <0%> (ø)	⬆️
plugins/publish-to-udata/geogw.js	0% <0%> (ø)	⬆️
lib/services/link-proxy.js	0% <0%> (ø)	⬆️
lib/got.js	0% <0%> (ø)
lib/api/routes/links.js	0% <0%> (ø)	⬆️
lib/api/middlewares/thumbnail-proxy.js	0% <0%> (ø)	⬆️
plugins/publish-to-udata/got.js	0% <0%> (ø)
plugins/publish-to-udata/udata.js	0% <0%> (ø)	⬆️
plugins/publish-to-udata/udata-proxy.js	0% <0%> (ø)
... and 2 more

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