added readme

README.md

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+## Grammar Syntax
+
+### Example
+
+    $FOO -> /foo  
+    $FOO -> /foo$FOO  
+    $FOO -> $BAR  
+    $BAR -> /bar  
+    $BAR -> $BAR  
+
+
+### Nonterminals
+
+A Nonterminal starts with a leading `$`. The nonterminal `FOO` would be written as:
+
+    $FOO
+
+
+### Terminals
+
+A Terminals starts with a leading `/`. The terminal `bar` would be written as:
+
+    /bar
+
+Note that `/ab` differs from `/a/b`. The string `/ab` resolves to the terminal `ab`,
+whereas `/a/b` resolves to the terminals `a` and `b`