Dagbladet.Headline (parseUrlDate): fix crash on unrecognised patterns

Apply Data.Text.init iff we were able to extract a result;
otherwise return empty result.
CLI: print usage on unrecognised command
Add a test-suite target
Dagbladet.Headline: expose parseUrlDate if building test suite
Two examples for parseUrlDate
Merge branch 'parse-url-specs' into specs
Merge branch 'fix-parse-url'
Merge branch 'specs'
Rename tests/Main.hs to tests/Specs.hs
Add .ghci