Represents the work of 5 commits

Fixes the atomic class slot names

o now all slot names of the atomic classes for the citation types
  are named after the class.

Puts "citation" slot in place for "eml"

This is related to issue #27

Adds more coercion methods for literature classes

o This belongs to issue #27

Changes documentation and inclusion

o Adds the modules to be included into the literature module
	- adds modules already there for inclusion
o changes the citation prototype in comments

defines XML/S4 coercions for citation class, corrects them for article class #27