Add rpm spec file

Tested on CentOS 5 and 6 against GitHub's 0.0.11 tarballs, so we
use sed hackery to patch changes from after 0.0.11. This should be
reworked to use tarballs produced by `make dist` instead.
Force CentOS 5 rpms to have el5 in release number
Add `make rpm` target

Add a make target for building rpms.
Put build artifacts in dist/

Keep git's root from being polluted with build garbage.
Add rpmbuild directory to gitignore
Rework `make dist` and `make rpm` targets

Add targets for the files that `make dist` creates and dump rpm
artifacts into the dist/ directory.
Tweak `make rpm`

Generate the rpm version from configure and the release number
from `git describe`.
Add more build artifacts to maintainer-clean

Clean up junk left behind by `make (dist|rpm|deb)` in
`make maintainer-clean`.
Add clicraft.spec to gitignore
Replace clicraft.spec.in with clicraft.spec

Generating clicraft.spec with autoconf causes `make rpm` to fail
when ./configure can't find the spec file in the dist directory
since we don't include that directory in the tarball. So just bump
the version on each update like we do with the debian changelog.
Update package info

Provide instructions for creating and installing packages on RHEL-
and Debian-based systems.