Fixed error in README file.
Fixed error in README file.

Previously the instructions said to create a symbolic link to the
RAMCloud client library located in obj.java-transactions, but since the
RAMCloud submodule is checked out in detached head state, the actual
directory is just "obj".

ellitron/ramcloud-gremlin,jdellithorpe/torc-gremlin,ellitron/ramcloud-gremlin,jdellithorpe/torc-gremlin