chore: fix build errors

[dyladan]

Fixes an issue that prevented lerna from being used on node 8.

• Switch from yarn to npm. This will install lerna even on node 8. note: technically we are installing a devDependency that is incompatible with node 8 (lerna), but it is ok because we don't use the feature which uses the broken module.
• Skip checking the broken link so build will pass.

todo: create a follow up PR that removes the skip of the broken link after it is published to npm #751

[OlivierAlbertini]

I'm reviewing this and on my branch I did exactly the same thing (without changing tdd script) and I get the same issue...

[dyladan]

looking into it

[codecov-io]

Codecov Report

Merging #747 into master will increase coverage by 0.27%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           master    #747      +/-   ##
=========================================
+ Coverage   96.22%   96.5%   +0.27%     
=========================================
  Files         208      67     -141     
  Lines        9488    1603    -7885     
  Branches      809     131     -678     
=========================================
- Hits         9130    1547    -7583     
+ Misses        358      56     -302

Impacted Files	Coverage Δ
...ges/opentelemetry-propagator-jaeger/src/version.ts	0% <0%> (ø)	⬆️
packages/opentelemetry-api/src/api/metrics.ts	53.33% <0%> (ø)	⬆️
packages/opentelemetry-core/src/common/time.ts	95.38% <0%> (ø)	⬆️
...opentelemetry-core/src/platform/node/timer-util.ts	50% <0%> (ø)	⬆️
...y-api/test/noop-implementations/noop-meter.test.ts	97.22% <0%> (ø)	⬆️
...elemetry-api/src/distributed_context/EntryValue.ts	100% <0%> (ø)	⬆️
packages/opentelemetry-core/src/version.ts	100% <0%> (ø)	⬆️
...ackages/opentelemetry-core/src/platform/node/id.ts	100% <0%> (ø)	⬆️
...core/src/context/propagation/BinaryTraceContext.ts	96.22% <0%> (ø)	⬆️
...try-propagator-jaeger/src/JaegerHttpTraceFormat.ts	95.65% <0%> (ø)	⬆️
... and 197 more

[dyladan]

@open-telemetry/javascript-approvers I know this has had a lot of updates but I just squashed it all down into two commits. Please take a look and review.

[mayurkale22]

Nice work, thanks for fixing the build.