Fix a typo in the "liber sync" invocation

README.md

@@ -92,7 +92,7 @@ To upload the contents of the local database (including the file
 contents themselves) to a remote `liber` server, run the following
 command:
 
-    $ liber sync=http://remote.server.address/
+    $ liber sync http://remote.server.address/
 
 
 ### Running the HTTP interface