More fixes to configuration.rst
Merge branch 'master' of https://github.com/macroevolution/bamm

Conflicts:
	doc/source/configuration.rst
Merge branch 'master' of https://github.com/macroevolution/bamm
Merge branch 'master' of https://github.com/macroevolution/bamm
Merge branch 'master' of https://github.com/macroevolution/bamm
merge
Merge branch 'master' of https://github.com/macroevolution/bamm
Merge branch 'master' of https://github.com/macroevolution/bamm
Merge
slight edit to configuration.rst to reflect tree requirements