Updated REGEX for quote marks

Updated REGEX to take into account both double and single quote marks

Detect an optimised encoded SVG

Updated encoded REGEX detection to take into account an already optimised encoded SVG

Valid input SVG

Merge pull request #3 from chrisboakes/bug-correct-typo

Ensured input SVG is valid

Fixed quotation bug

Encoded single quotation marks need to be wrapped in a double quote mark or else invalid.