Merge pull request #3 from euccastro/master

add syntax tests
Split the lexemes tests into several source files. This change makes test failures better reported, because non-conforming interpreters (Bronze Age and Klink) can parse the main source file of the group lexemes.k without errors.
Improve comments in the source code.
Update authors list.
Merge pull request #4 from euccastro/master

test $if, begin to test pairs-and-lists and environments, other fixes
Define list of optional modules supported by the system under test. Declare required optional modules in test group metadata.