* allow passing opts to Histogram and Summary from client. w/ burnettk
* default opts to nil and let collector create the hash when needed and added client tests for it. w/ burnettk
When reusing the same client in different places to export the same
metric, there is no external interface to retrieve this metric after
it's registered. Using `instance_variable_get` to reach into the
instance variable `@metrics` is less preferable. Re-registering the
metric will lead to an ever-growing array of `@metrics`.
This commit provides a way to get the metric by name, and optionally by
type and help, so that we can use the registered metric(s) to observe
Alan Guo Xiang Tan
Sam Saffron
Anuj Biyani
jasquat
Hector Zhao