Improved Swedish localization courtesy of translator colleague

The old version says: "If you think [app name] is a useful tool...",
but that doesn't reflect the tone or meaning of the original English
version, and it's not appropriate for games and many other kinds of
apps. The new Swedish version matches the English "If you enjoy using
[app name]..." version.
Merge pull request #151 from linguafranca/swedish

Improved Swedish localization courtesy of translator colleague