Perf with JMH

[abersnaze]

#776 This is a small change on top of perf with Caliper to performance benchmarking with JMH.

[abersnaze]

Example output of the same timings done in #788

Benchmark                                  Mode Thr     Count  Sec         Mean   Mean error    Units
r.o.ObservableBenchmark.timeBaseline      thrpt   1        20    1      557.493       12.025   ops/ms
r.o.ObservableBenchmark.timeMap           thrpt   1        20    1      374.152        3.968   ops/ms
r.o.ObservableBenchmark.timeMapIterate    thrpt   1        20    1     2389.195       42.686   ops/ms

BUILD SUCCESSFUL

Total time: 2 mins 5.172 secs

[cloudbees-pull-request-builder]

RxJava-pull-requests #758 FAILURE
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[benjchristensen]

Thanks, I look forward to seeing our perf testing mature in this project.

[benjchristensen]

Related to #776