Add apex/log benchmark

[osamingo]

Add apex/log benchmark.

BenchmarkApexLogAddingFields-8                    100000             16614 ns/op            3609 B/op         63 allocs/op
BenchmarkApexLogWithAccumulatedContext-8          100000             14201 ns/op            2385 B/op         48 allocs/op
BenchmarkApexLogWithoutFields-8                   500000              3048 ns/op             584 B/op         11 allocs/op

[coveralls]

Coverage remained the same at 96.352% when pulling 02fb051 on osamingo:add-apex-log-benchmark into 07c03a1 on uber-go:master.

[akshayjshah]

Nice - thanks for the contribution, @osamingo! Two things:

1. Before we can merge this, you'll need to sign Uber's Contributor License Agreement. Please take a look and let me know if you have any questions.
2. Please revert the changes to the README - since the apex/log benchmarks weren't run on the same machine as the others, they're not comparable. Once the rest of your code is merged, I'll run the new benchmarks on my machine and update the README.

[coveralls]

Coverage remained the same at 96.352% when pulling 82a6090 on osamingo:add-apex-log-benchmark into 56e3723 on uber-go:master.

[coveralls]

Coverage remained the same at 96.352% when pulling 6ef82ba on osamingo:add-apex-log-benchmark into 56e3723 on uber-go:master.

[osamingo]

Before we can merge this, you'll need to sign Uber's Contributor License Agreement. Please take a look and let me know if you have any questions.

OK. I confirmed CLA.

Please revert the changes to the README - since the apex/log benchmarks weren't run on the same machine as the others, they're not comparable. Once the rest of your code is merged, I'll run the new benchmarks on my machine and update the README.

You’re right. I reverted it.

[akshayjshah]

Awesome - thanks!