Updated readme's, add prototype function declaration operation

ast/var_table.go

@@ -121,3 +121,15 @@ func DeleteVarTable(table VarTable) {
         }
     }
 }
+
+func RemoveVar(arg string, table VarTable) {
+    if SyncTablesWithOSEnviron {
+        err := os.Unsetenv(arg)
+        if err != nil {
+            log.Log(log.DEBUG,
+                "Failed to remove "+arg+" from env: "+err.Error(),
+                "vartable")
+        }
+    }
+    delete(*table, arg)
+}