Extracting Date, Time and Datetime from ruby-hl7

The methods "to_hl7" used to be on ruby-hl7 file.
Also, did some refactoring for reducing
the code duplication.   Before that, I've added
some test.
Adding .travis.yml file
Fixing the path for the string class
Moving HL7::Message::Segment to it's own file.

Also adding a spec_helper file and updating the specs to use it.
Moving has_children dynamic method creation into separated methods
Merge pull request #1 from mogox/refactoring

Refactoring
Upgrading rake, spec and using simplecov

Trying to move things for ruby 1.9.1 and above
Adding rdoc gem for rbx
Fixing the Travis-ci image
Rubinius throws a different error for...

Method missing.  I'm trying to fixing the
spec by adding a special case for rbx.

This commit also includes more refactoring
on the segment file.
Extracting the Segment "children" related methods

Created a new module with those methods and minor
refactoring in date_time.
Adding test for the SegmentListStorage module
Moving message to an individual file
Extracting the batch parse methods from HL7::Message
moving MessageBatchParse module to its own file
Moving parse instance methods into HL7::MessageParser module
Creating a MessageParser class and a module for the batch parser
Extracting  methods to generate segments from Message

Also minor refactoring in other classes.
Extracting the segment delimiter setup into a method

The segment initialize initalizes the segment and item
delimiters but now using the method setup_delimiters
loading the required files on ruby-hl7

Aslo some cleanup