added support for % operator
Ignore RVM config files
Add more specs
Update documentation
Change the definition of a function to an identifier followed by an open parenthesis

This will make it a little easier to add more functions in the future.
Merge branch 'master' of github.com:CraigCottingham/dentaku
Add method_missing and respond_to_missing? to TokenMatcher

This will facilitate adding arbitrary functions at runtime. I don't much like returning true for everything in respond_to_missing?, so maybe a lookup table should be added later.
Add self.add_rules to Rules to add new rules to the rulebase

New rules need to be added to the *beginning* of the rulebase. Is this a precedence thing?
Add add_rules method to Calculator
Add initial support for calling external functions to Evaluator#evaluate_step()
Add external function bodies to Rules
Return self from Calculator#add_rules()

Enables chaining.
Add specs to test external functions
Move more of the function's token pattern into Rules.add_rules
Merge branch 'external_funcs' of github.com:CraigCottingham/dentaku into external_funcs