Implement standard release procedure for exporters + add version cli flag

Implement standard release procedure for prometheus exporters. Use CircleCI to build new binaries using promu and release to github, docker and quay.

Will be useful for the following commits, by allowing the standard release procedure for prometheus exporters.

Fix to make DockerImage run anywhere

Added Dockerfile, updated README

Use github.com/prometheus/common/log

github.com/prometheus/log is an old package, migrate to use "log" within
common.

Scoreboard provides a more detailed breakdown of worker status, export and
parse that too.

In line with other exporters, add an apache_up gauge to describe whether Apache
server can be reached or not.

added support for connection data

Allow string values in mod_status' output.

fixed the number of metrics

Update default insecure flag setting in README

Rename uptime_seconds to uptime_seconds_total.
Delete requests_per_second, sent_per_second_bytes, request_size_bytes as
they can be calculated by prometheus.