Use used price if there's no new price for Amazon.
Store cart/shortlist in localStorage.
Merge pull request #30 from drabinowitz/localStorageShortlist

Store cart/shortlist in localStorage.
Use used price if there's no new price for Amazon.
Clarify comments.
Merge branch 'amazon-bug' of https://github.com/jDeppen/TechnoSave into amazon-bug

Conflicts:
	js/api-amazon.js
Merge pull request #29 from jDeppen/amazon-bug

Use the used price if there's no new price for Amazon.