Release/1.2.0 (#46)

* add release-* target to Makefile

* prepare release 1.2.0

Prepare version 1.1.2 (#38)

prepare version 1.1.1 (#33)

* bump version: 1.1.0 → 1.1.1
* make changelog release

Prepare version 1.1.0 (#29)

* bump version: 1.0.0 → 1.1.0
* prepare changelog
* update documentation

provide auto registration facility for collectors (#18)

To provide more than one simple collector we refactor the registration
of collectors to do this automatically.
From now all collectors that follows the convention for new collectors.
We also add a real life collector for load average (1, 5, 15).
Finally we prepare the new major release.

add Changelog (#17)