No error 500 for nonexistent cities

Added default behavior for trying to get weather of invalid
(nonexistent) city instead of showing error 500 page.

Fix code style

Conflicts:
	src/main/webapp/index.ftl
Merge pull request #5 from AlexWyrm/master

No error 500 for nonexistent cities
unit of measurement for temperature added
sample request: http://localhost:8080/moscow/ru/F