add a path helper to work with wiki-paths.
perform some minor Gemfile updates.
extract expander into its own class.
replace seamless-test with helpful readable method.
let expand return the string of the expansion

Instead of directly printing to stdout expand
now returns the full expansion. It is now up
to the caller to decide what happens with the
expansion (in our case we still print it).
handle absolute paths as parameters for expand.
do not try to expand page-links which are titles

also do not generate a seam for the top-level
parent page.
use path helper in renamer.
move renamer and expander classes into own files.