fixed 10cent-rounding-Bug for tips
used round(1) instead round
added tip-config
applied hints from breunigs to tip-config…
tip-patch fixes (things to make xeen happy)
search subcategories (fixes #5)

This patch doesn’t have a test because capybara-webkit has weird
event handling, which seems to fire for the previous page load
instead of the current one. This leads to the last page not being
searched. Unfortunately the example shop only has subpages on the
last top category, so it doesn’t fire.

It works fine in Firefox/Chrome, so I’m committing anyway.

Late night commits… yaaaay
Merge pull request #10 from joker234/tip-patch

make tips configurable and round tips to 10cents