Add carbon-aggregator support

Commits related to `carbon-aggregator` from issue #44:
* Added **carbon-aggregator** support (881cf32).
 * Added tests (47b6649).
* Added **storage-aggregation.conf** support (18c77a9).
* Added **aggregation-rules.conf** support (d334d07).
 * Configuration **example** added to the README (e60036e).

Bonus:
* **Tests** for checking **\*-rules.conf** files content (6d16fa6).
* README, tests: relay-rules example fixed (5175111).