Allows one to change the parser configuration. That allows the end-user to define the tag he wants.
Examples in CustomTagsTest.
Fix null comparison in RelationalOperations
Change return type of RelationalOperations eq and neq to boolean

Not sure why the return type was Object, boolean can always be assigned to Object thanks to coercion?
Merge pull request #71 from lyncodev/custom-tag-syntax

Custom tags
Test for issue #75
Merge pull request #74 from supergillis/master

Fix null comparison in RelationalOperations
Fix for issue #75.
Merge pull request #81 from lyncodev/issue75

"is" operator to support selection expressions
Played stories #79 and #80.
Fixed broken tests
Merge pull request #83 from lyncodev/allowing-undefined-values

Evaluation system to allow undefined values
#77 Added range function
Merge pull request #87 from realcnbs/range-function

#77 Added range function