Support for collection.media and other improvements

• Enable installation via collection.media.
• Support line feeds, such as in pre blocks
• Add data-cloze-keep-regex option to override the regex that determines what parts of the text should not be replaced with blanks. Add … to the default regex for this. Thanks rwmpelstilzchen!
• Add CSS class for current cloze on backside to enable highlighting.
• Fix bug where backticks wouldn't be removed in other clozed values.
• Additional configuration options (data-cloze-replace-char, data-cloze-replace-same-length, etc.)