Allow picture render size to be flexible in width or height

Before, you had to state render sizes in the format '300x200'.

Now, you can use e.g. '300' for inferring the height from the image file preserving the aspect ratio (or 'x200' for inferring the width).

These two additional ways of specifying the image geometry are provided by the used image processing library Image Magick (and its wrapper dragonfly), see http://www.imagemagick.org/script/command-line-processing.php#geometry.
Revert "Allow picture render size to be flexible in width or height"

This reverts commit c0f18802f69b1c516cef135d25ca9cb10ff402b8.
Adds feature spec for sitemap option in page configuration
Adds feature specs for the configuration form of normal and global pages.
Adds feature spec for page tagging configuration form view.
Adds short paragraph about testing Alchemy
Refactors and cleaning up javascript translations.
Changes the initialization of tinymce configuration. Closes #500
Use `alchemy_display_name` to represent the currently logged in user.

To make this better adoptable for applications hosting Alchemy or engines, we do not assume `name` on the user class.
Adds a char counter js class.
Adds char counter to page title and meta description fields.
Updates links to latest Alchemy version and live demo.