Merge branch 'release/0.2.0'

* release/0.2.0: (147 commits)
  Add README
  Fully reversible versions
  Update to latest libcork and clogger
  Avoid double-free in cached PDB
  `pacman -Sddp` to check for packages on Arch
  Perform `git reset` in correct directory
  No hidden parts in Buzzy versions
  Use yum's `--cacheonly` option
  Don't build package before uninstalling
  RPM spec requires spaces around `>=`
  Allow distros to override default global variables
  Additional installation prefix variables
  Autotools builder
  Better comparison of numeric version parts
  Access variables in linked repositories
  Empty $PREFIX/share/buzzy/config.yaml
  Configuration files that override global defaults
  Forward SSH agent to Vagrant VMs
  RPM packager
  Don't use `cmake --target`
  ...