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.