chore(benchmark): remove test for generateReportPartial
feat(benchmark): add statistical functions to calculate confidence interval
feat(benchmark): add confidence and stability info to averages
feat(benchmark): calculate relative margin of error and simplify report
fix(benchmark): fix standard deviation calculation

Previous algorithm was dividing total of squares by sample length,
where it should have been dividing by sample length minus 1
feat(benchmark): add standard deviation to report
chore(benchmark): remove interpolateHtml method
chore(benchmark): remove redundant getAverages method
refactor(benchmark): move all methods/props to appropriate namespaces
fix(WatchGroup): Handle watching elements of array that were removed.

Closes #1046
feat(Scope): Instrument Scope to use User tags in Dart Obervatory

Closes #1138
feat(benchmark): calculate coefficient of variation
refactor(benchmark): reduce complexity, and move formatting of values into template
refactor(benchmark): reduce code redundancy for statistics calculations
feat(benchmark): improve layout of data by moving averages to dedicated row
test(annotion_src_spec): re-enable tests failing due to dartbug 19177

It has been fixed in 1.5.0-dev.4.5

Closes #1150
feat(http): run interceptors synchronously until first non-sync interceptor