Working version
Fixed a bug in the reset, where field would just pile up on repeated
resets
Fixed spelling error
Changed application title
Now emptying fields upon error so misunderstandings on relations
between entered and previously found data are avoided
Added handling of emty fields and added placeholders for text fields
Since we now use the warning CSS also, it has to be added to the
cleanup/reset part
Added use of glyph icons
Fixed bug with multiple selection boxes being appended
Fixed a bug when going from city with multiple zipcodes to a unique
city/zipcode combination
Cleared out some unnecessary code after reading the docs on
Params::Validate
Removed debugging statement, no longer useful
Added some test of the newly implemented methods:

- get_postalcode_from_city
- get_city_from_postalcode