added def to make a _msg without data or size
added def to make msg with a specific size
added def to make message with bytestring
removed documentation and make corrections so that it's almost functional
added documentation
correctly msg_init'ing msgs
refactor creating the ptr and tagging it into helper procedure and using
it place of all the calls to malloc and set-cpointer-tag!
documentation has links
added unit tests to new message creation procedures
Merge pull request #4 from neomantic/msg-creation-defs

Msg creation defs