(doc) Describe back conversion.

Author: LittleHelicase

README.md

@@ -1,6 +1,6 @@
 # graphlib2dot
 
-This command line tool takes a graphlib JSON document and converts it into a
+This command line tool can convert between a graphlib JSON document and a
 dot file.
 
 ## Installation
@@ -25,5 +25,12 @@ Or specify a file:
 graphlib2dot -f graph.json
 ```
 
+You can also convert in the other direction:
+
+```
+cat graph.dot | dot2graphlib
+dot2graphlib -f graph.dot
+```
+
 You can create a JSON representation of your graphlib Graph via
-`graphlib.json.write`. More info [here](https://github.com/cpettitt/graphlib/wiki/API-Reference#json-write).
+`graphlib.json.write` and deserialize them via `graphlib.json.read`. More info [here](https://github.com/cpettitt/graphlib/wiki/API-Reference#json-write).