Release 1.4.0

• Migrated project to Xcode 9.3 and Swift 4
• Bug fixes (esp. in syntax-rules)
• Fixed logic for referencing unquote, etc. in backquote.
• Include native date/time operations and functionality for accessing user data
• Native support for a few common string functions
• Support for read-token (generalization of read-line)
• Added libraries (lispkit stack), (lispkit queue), (lispkit logic)
• Implement bitwise operations for exact integers of arbitrary size
• Complete rewrite of the error reporting and representation sub-system
• Preparations for managing source locations