Bump version from 0.5.3a2 to 0.5.3a3

Merge pull request #75 from oemof/revision/clean_up_energy_system

Revision/clean up energy system

Release v0.5.2

Fix wrong URL in README.rst for packaging badge

Merge pull request #66 from oemof/v0.5

Release v0.5.1

Release v0.5.1b2

Release v0.5.1b1

Reverse order in HierachicalLabel

This way, label[0] is always the local name.
This should be better than label[-1].

Merge pull request #53 from oemof/features/add-subnetworks

Add subnetworks

Release v0.5.0