[BUGFIX] Fix SQL GRANT syntax in .travis.yml (#31)

There was a double set of single quotes for the host name,
and the user name was not quoted at all.

Author: oliverklee

.travis.yml

@@ -35,7 +35,7 @@ before_install:
   echo;
   echo "Creating the database and importing the database schema";
   mysql -e "CREATE DATABASE ${PHPLIST_DATABASE_NAME};";
-  mysql -u root -e "GRANT ALL ON ${PHPLIST_DATABASE_NAME}.* TO ${PHPLIST_DATABASE_USER}@''%'';";
+  mysql -u root -e "GRANT ALL ON ${PHPLIST_DATABASE_NAME}.* TO '${PHPLIST_DATABASE_USER}'@'%';";
   mysql ${PHPLIST_DATABASE_NAME} < vendor/phplist/phplist4-core/Database/Schema.sql;
 
 install: