Gather profiles globally for the entire run

[Manfred]

An object representing a run or perf_check could keep all the profiles. Then perf_check.profiles could return all the measurements. Statistics code and figure out how to interpret depending on the report (ie. compare branches, compare paths, compare responses).

[
  { branch: 'master', request_path: '/companies', latency: 0.23, query_count: 23, status: 200 },
  { branch: 'master', request_path: '/companies', latency: 0.27, query_count: 23, status: 200 },
  { branch: 'slower', request_path: '/companies', latency: 0.56, query_count: 37, status: 200 },
  { branch: 'slower', request_path: '/companies', latency: 0.66, query_count: 37, status: 200 }
]