Handle FileNotFoundError. Closes #44

Using `IOError` for compatibility, from Python 3.3 `IOError` is alias of `OSError`
https://stackoverflow.com/a/28633573/6202405

Checking the errno of 'No such file or directory' so that only that exception will be catched.
https://docs.python.org/2/library/errno.html
https://stackoverflow.com/a/39414133



Signed-off-by: Bhavin Gandhi <bhavin7392@gmail.com>

Normal errors should be displayed by default, even if they are not
catastrophic.

It looks like py26 gets less and less support by more and more core
packages.

Yet we can pin old `pytest` and `setuptools` versions but in the long
run we will drop support for python2.6 and python 3.3 too.

Tell about using real dice with more than 6 faces.

The manpage test failed when tests were run in a long path. The help
output then led to an extra line break which made comaparisons quite
cumbersome.

This one ruined the 0.9.2 release.

Use version generated by docutils from manpage template in `docs/`.

The wordlist length must be a power of the number of dice sides used to
result in fair choices. This is not being relatively prime.

Tell about problems with wordlist lengths and dice side numbers.

Put this list into list of all contained wordlists and provide a link to
the source.

Mark it properly as github username.

Also fix entropy computation.

Begin with some very plain usage samples.

Avoid to write down a certain path, as that could block reproducible
builds.

in man page.

We will have another release soon. So, let's care for details better to
soon than too late.

The documenting comment (starting with ``#: ``) is neccessary for vars
and constants only. All these comments are used by `Sphinx` to generate
documentation.