Version 1.3b

• Upgraded version to 1.3b
• Sanitized comparison between mapping pairs in prolongables check
• Removed use of std::string::npos
• nontrivial member is determined by arithmetic rather than counting
• Fix isTrivial member of parihkVector for alphabet sizes greater than 2
• New and faster algorithm for counting occurences of a character in a word for a given alphabet
• Added missing documentation to prefix.hpp
• parihkVector::operator std::string() is now const
• Removed comparison members of parihkVector to use the default instead.