Fix ambiquity due to generalised `elem`

In base-4.8, `elem` has been generalised to `Foldable`, so in
combination with `-XOverloadedStrings`, something like `(elem "abc")`
can't be inferred anymore.

Fixes #41
Adding some files to the ignore list
Merge branch 'pr-base47' of git://github.com/hvr/hastache into hvr-pr-base48
Updating the ChangeLog