Kudos to @drebs for another fine patch.

Looks like we need the '.py' filename extension to call `rst2man` in
regular installs.

Use function to get wordlists dir. Fixes #38

The path to wordlist files is hardcoded in the generated sphinx
documentation and because it may differ depending on how the package is
installed this creates different problems:

  - the path hardcoded in the online api documentation may differ from
    the one in each installation, leading to incorrect information
    provided to the user of the api.

  - packaging diceware documentation to specific operating systems may
    generate unreproducible packages.

This commit replaces the variable WORDLISTS_DIR by a function called
get_wordlists_dir() that delays the construction of the path instead of
doing it during module loading.

We showed an outdated list of available wordlists before.

Apparently `pypip.io` is not longer active. It looks like `shields.io`
offers even much more badges.

`sphinx` can generate not only HTML docs but also man pages. Let's see
how far we can go to replace the more or less manually crafted man page
we provide currently.

In fact Arnold G. Reinhold copyrighted each of the pages of the
`diceware.com` website. The idea as such was not copyrighted (and might
be uncopyrightable).

Mr. Reinhold, however, still owns a "diceware" trademark.

And remove unneccessary whitespace.

We should be able to generate a more accurate man page for `diceware`.
with `docutils` and `rst2man` we can create a nice looking man page with
proper styles set.

Yet, we onlyy provide first parts of the man page template.

Make Sphinx stop complaining and fix indents.

We do not accept open filedescriptors as argument for `WordList`
anymore. This seems to be the only way to make sure we can open/close
wordlist files whenever we want.

Use path instead of filedescriptor with `WordList`.

We will not accept filedescriptors as `WordList` arguments anymore.

We will not accept filedescriptors as `WordList` arguments anymore.

We do not need to test `infile` as file descrtiptor, as we expect paths
(strings) from now on.

Do expect file paths instead of already opened filedescriptors.

The `argparse.FileType` type is considered bad style. Cf.
http://bugs.python.org/issue13824. With this FileType we cannot tell
when to close a file after reading (which should be done for most
regular wordlists) or not (in case of input from stdin).

Stop py.test complaining.