Update README

README.md

@@ -17,34 +17,41 @@ Steps:
     cd build
     cmake ..
     make
-    
+
 ## Usage
 
-    protobuf-spec-comparator dir1 file1.proto dir2 file2.proto type-name
+    protobuf-spec-comparator dir1 file1.proto dir2 file2.proto type-name [--binary]
+
+The program takes 5 arguments:
 
-The program takes 5 parameters:
 - dir1: A directory containing .proto files
 - file1.proto: The relative path of a .proto file in dir1
 - dir2 and file2.proto: The same as above for another version to compare.
 - type-name: The name of a message or enum defined in file1.proto and file2.proto
 
-The definition of a message or enum type-name in file1.proto and file2.proto is compared as detailed below.
+You can add the following options:
+
+- `--binary`: Report compatibility of the binary serialization as opposed to the JSON serialization or similar. See below for details.
+
+### Behavior
+
+The definition of a message or enum `type-name` in file1.proto and file2.proto is compared as detailed in the following sections.
 
 If type-name is just ".", then all the messages and enums in file1.proto and file2.proto are compared.
 Added and removed messages and enums are reported.
 
 ### Message comparison
 
-Message fields are matched by name (a binary comparison mode will be added where fields are matched by ID number).
+Message fields are matched by name (default) or by number (when using `--binary`).
+
 Fields present in file1 and missing in file2 are reported as removed, and vice-versa for added fields.
 Any changes in matching fields are reported.
-If matching fields both have an enum or message type, then those enums and message types are also compared.
+
+If two matching fields both have an enum or message type, then those enums and message types are also compared.
 
 ### Enum comparison
 
-Enum types are compared as follows.
 Enum values are matched by name (a binary comparison mode will be added where values are matched by ID number).
+
 Values present in file1 and missing in file2 are reported as removed, and vice-versa for added fields.
 Any changes in maching enum values are reported.
-
-