Hoogle v5 uses a different json representation for the data, requires a
new URL and also contains HTML markup inside the json fields.

This commit removes all markup to be able to handle the hoogle responses
using the same structure as with the previous response structure (from
hoogle v4).

Add `-Wunused-do-bind -Wunused-local-binds -Wunused-top-binds -Wunused-matches`
and fix all the things.

Add `-Wmissing-signatures` to `ghc-options`.

Add `-Wincomplete-patterns` to the `ghc-options` field of the cabal file
and fix all warnings.