Add optional redis dependency to setup.py (#399)

* add optional redis dependency to setup.py

* update installation documentation

* clarify docs and add redis to dev install

README.md

@@ -114,6 +114,19 @@ period via the --process-timeout flag. E.g.,
 nosetests --processes=8 --process-timeout=120 tests/test_binaries.py
 ```
 
+### Redis
+
+If you'd like to use redis for state serialization (instead of disk), install
+redis using your host package manager, then install manticore as above, but
+with `[redis]` appended to the name of the package, e.g.
+
+```
+pip install manticore[redis]
+```
+
+Note that this does not make manticore use redis automatically, and you'll still
+have to manually set the workspace to the redis URI.
+
 ## Usage
 
 ```

setup.py

@@ -19,6 +19,10 @@ setup(
             'coverage',
             'nose',
             'Sphinx',
+            'redis',
+        ],
+        'redis': [
+            'redis',
         ]
     },
     entry_points={