RST docstrings in Bio/Graphics/Comparative.py
Resolve slash-n in RST docstrings.

Solves temporarily disabling RST markup as of commit
3cfb6334a17ce8b783c93f8e00baf214cdcb8668 by the simple
trick of putting the docstrings in raw string mode.
RST docstrings for Bio/Graphics/GenomeDiagram/_FeatureSet.py
RST docstrings for KDTree.

Changed the numpy.random import to solve this epydoc warning:

$ epydoc -v -o ~/api -u http://biopython.org -n Biopython Bio/KDTree
Warning: Module Bio.KDTree.KDTree is shadowed by a variable with the same name.
Warning: Failed identifier crossreference targets:
         - (b-a)
               (from Bio.KDTree.KDTree'.random)
         - a
               (from Bio.KDTree.KDTree'.random)
         - random_sample
               (from Bio.KDTree.KDTree'.random)

Now all we have is the shadowing warning.
Convert test_KDTree.py to use unittest