RFC 3986 unreserved characters

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http://tools.ietf.org/html/rfc3986#section-2.3

RFC 3986 section 2.3 Unreserved Characters (January 2005)
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
a b c d e f g h i j k l m n o p q r s t u v w x y z
0 1 2 3 4 5 6 7 8 9 - _ . ~