Move docstrings above `from __future__` imports.

Docstrings are considered as such by python only if they are the first
statement in the file/block.  Even if they are preceded by a
`from __future__` import they are interpreted as just a string.
Merge pull request #245 from x746e/moved-docstrings-to-the-top

Move docstrings above `from __future__` imports.