Common libraries for Prometheus components

 This package includes:
 .
  * github.com/prometheus/common/config: Common configuration structures.
  * github.com/prometheus/common/expfmt: Decoding and encoding for the
    exposition format.
  * github.com/prometheus/common/log: Wraps https://github.com/Sirupsen/logrus
    in order to add line:file annotations to log lines, as well as to provide
    common command-line flags for Prometheus components using it.
  * github.com/prometheus/common/model: Shared data structures.
  * github.com/prometheus/common/promlog: Defines standardised ways to
    initialize Go kit loggers across Prometheus components.
  * github.com/prometheus/common/route: A routing wrapper around
    https://github.com/julienschmidt/httprouter using `context.Context`.
  * github.com/prometheus/common/version: Version information and metrics.