add czech localization

[saxicek]

Added czech localization. Was not able to build and test because of error in my babel installation (see below). Will appreciate if you try my change anyway and merge if everything works.

> babel-node build-browser && npm run minify

module.js:341
    throw err;
    ^

Error: Cannot find module 'lodash/lang/isFunction'

[coveralls]

Coverage remained the same at 99.087% when pulling c698274 on saxicek:master into 9c9220a on chriso:master.

[chriso]

Thanks.