Trying to make YARD extension slightly more robust
Correct Markdown syntax in Hamster::Enumerable
Don't mark Hamster::Enumerable as @private

...Because if we do, its methods are not listed among the methods of the
classes with include it.
Move #group_by to Hamster::Enumerable. Vector#group_by is now supported
Mark monkey-patched #sort for RBX compatibility as @private

This definition is supplied to work around a bug in Rubinius. But I don't want
the comment to appear as a docstring in the Hamster::Enumerable Yardocs.
Clarify Hash#sample docstring
Annotate return value of Set#sort
Hash#put spec should use #put
Edited docstring for Hamster::List
Write docstrings for a few more Vector methods