DOC: sphinx Didn't find <class attribute> in <module> when building docs

[fkuehlein]

class added in #156, but missing in docs/source/api/climate

[fkuehlein]

while at it, might also look into countless cases like

reading sources... [ 50%] api/core/network
Didn't find Network.N in pyunicorn.core.network

when building docs.

This happens for class attributes only, not for class methods. Yet, all attributes appear alright in the built documentation, so it doesn't cause an actual issue. Using .. autoclass:: instead of .. automodule:: e.g. in api/core/network.rst will fix the warning, but doesn't really apply here as we want to document modules.

[fkuehlein]

The original issue has been resolved as of #232, but the issue in the above comment persists, although it is only a matter of having a clean build log.