Add missing dependency on alembic.

README.md

@@ -28,6 +28,7 @@ $ apt-get install redis-server
 3. Create database
 ```
 $ ./manage.py db.init
+$ alembic stamp head
 ```
 
 ## Running the aprs client and task server

requirements.txt

@@ -4,3 +4,4 @@ coveralls==0.4.4
 geopy==1.11.0
 manage.py==0.2.10
 celery[redis]>=3.1,<3.2
+alembic==0.8.3