adds crystals parser code

lib/parser/function_definition.rb

@@ -0,0 +1,17 @@
+module Parser
+  module FunctionDefinition
+    include Parslet
+    
+    rule(:function_definition) {
+      keyword_def >> ((module_name|instance_variable|name).as(:receiver) >> str(".")).maybe >> #possibly qualified
+                  name.as(:function_name) >> parmeter_list.maybe >> newline >> expressions_end >> newline
+    }
+
+    rule(:parmeter_list) {
+      left_parenthesis >>
+        ((name.as(:parmeter) >> (comma >> name.as(:parmeter)).repeat(0)).repeat(0,1)).as(:parmeter_list) >>
+      right_parenthesis
+    }
+
+  end
+end