Chaperone

Refinements:

- Create a special-case syntax for shell escapes: ``$(`shell-command`)`` mainly to
assure that such syntaxes are propery supported instead of being expanded as a
side-effect. Previously, the syntax above would treat the result of the command
as the name of an environment variable, and since it was not found, would insert
the results. Since it was a useful trick, formalizing the use and eliminating
edge cases was important.
- Disabled shell escapes by default in ``envcp`` and added the ``--shell-enable``
switch to enable them.
- Added further documentation about shell escapes to clarify exactly how they
work and how they should be used.

Enhancements:

- Added documentation for ``envcp`` in the new utilities section of the documentation.
- Enhanced environment-variable expansions so they are smart about nesting.
- Fixed syslog receiver so that trailing newlines are stripped (programs like ``sudo``
and ``openvpn`` terminate their log lines this way, even though it is a questionable
practice).

Enhancements:

- Added the ``:/`` regex substitution expansion option, which provides a more extensive and useful
feature set than the bash-compatible options.
- Updated the documentation to reflect the new expansion option and added a footnote about
bash compatibility.

Enhancements:

- Added the ``:?`` and ``:|`` environemnt variable expansion options. The first works similarly
to bash and raises an error if a variable is not defined. The second adds more versatility to
expansions by allowing the expansion to depend upon the particular value of a variable.
- Added documntation for the above.

Bug Fixes:

- Made `setproctitle` an optional install so that `--no-install-recommends` can be used
on `apt-get` installs to streamline image size ([1, mc0e](https://github.com/garywiz/chaperone/issues/1))

Other:

- PyPi distribution is no longer done in "wheel" format, since that limits the ability
to include optional dependencies. Source format is used instead.