add integration tests against bundlers and browsers

[bmeck]

Please CIRCLECI please work.

See https://github.com/DataDog/dd-trace-js/pull/1674

[codecov[bot]]

Codecov Report

Merging #1723 (0e519e9) into master (cf9bc9c) will not change coverage. The diff coverage is n/a.

:exclamation: Current head 0e519e9 differs from pull request most recent head ddd7bd5. Consider uploading reports for the commit ddd7bd5 to get more accurate results

@@           Coverage Diff           @@
##           master    #1723   +/-   ##
=======================================
  Coverage   93.14%   93.14%           
=======================================
  Files         158      158           
  Lines        6706     6706           
=======================================
  Hits         6246     6246           
  Misses        460      460           

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[tlhunter]

It looks like this PR ended up a bit stale and there were some open queries. Is this something you're still working on or is it safe to close for now?

[tlhunter]

I'll close this PR for now but we can consider reopening it in the future.