Adding detailed readme

README.md

@@ -1 +1,55 @@
-Rules engine written with the help of antlr and golang
+# Golang Rules Engine
+Rules engine written in golang with the help of antlr.
+
+This package will be very helpful in situations where you have a generic rule and want to verify if your values (specified using `map[string]interface{}`) satisfy the rule. 
+
+
+Here are some examples:
+
+```
+  type obj map[string]interface{}
+  
+  parser.Evaluate("x eq 1", obj{"x": 1})
+  parser.Evaluate("x lt 1", obj{"x": 1})
+  parser.Evaluate("x gt 1", obj{"x": 1})
+  
+  parser.Evaluate("x.a eq 1 and x.b.c le 2", obj{
+    "x": obj{
+       "a": 1,
+       "b": obj{
+          "c": 2,
+       },
+    },
+  })
+  
+
+  parser.Evaluate("y eq 4 and (x gt 1)", obj{"x": 1})
+
+  parser.Evaluate("y eq 4 and (x IN [1 2 3])", obj{"x": 1})
+
+  parser.Evaluate("y eq 4 and (x eq 1.2.3)", obj{"x": "1.2.3"})
+  
+```
+
+## Operations
+All the operations can be written capitalized or lowercase (ex: `eq` or `EQ` can be used)
+
+Logical Operations supported are `AND OR`
+
+Compare Expression and their definitions:
+```
+eq: equals to 
+ne: not equals to
+lt: less than 
+gt: greater than
+le: less than equal to
+ge: greater than equal to 
+co: contains 
+sw: starts with 
+ew: ends with
+in: in a list
+pr: present
+not: not of a logical expression
+```
+
+