* Add averaging option to AMI and NMI

Leave current behavior unchanged

* Flake8 fixes

* Incorporate tests of means for AMI and NMI

* Add note about `average_method` in NMI

* Update docs from AMI, NMI changes (#1)

* Correct the NMI and AMI descriptions in docs

* Update docstrings due to averaging changes

- V-measure
- Homogeneity
- Completeness
- NMI
- AMI

* Update documentation and remove nose tests (#2)

* Update v0.20.rst

* Update test_supervised.py

* Update clustering.rst

* Fix multiple spaces after operator

* Rename all arguments

* No more arbitrary values!

* Improve handling of floating-point imprecision

* Clearly state when the change occurs

* Update AMI/NMI docs

* Update v0.20.rst

* Catch FutureWarnings in AMI and NMI