Header scroll improvements.

Resolves #12 and also adds more checks to improve the scrolling effect of the image header and text.
Add grunt task for translations.
Remove old translation files.
Remove posted on template tag.

We are not using this template tag in the theme; as such, there is not need for it to exist.
Add new language translation file.
Merge branch 'translations' of github.com:kopepasah/eighties into translations