Update docs for MariaDB support.
Fix BinlogStreamer for MariaDB.
Now vttablet can start without mysqld running, even in healthcheck mode.

So the mysql port is completely optional. We still try to backfill it
when we can, but it's never fatal.
Merge branch 'master' of github.com:youtube/vitess
InitializeConnections works on serving tablet types only.
Add note about setting VT_MYSQL_ROOT if necessary.
Fix logic in InitializeConnections
Merge branch 'liguo'
bug fix in schema reload

Now that schema reloads can be triggerred within
one second, we have to conservatively include the
last second to account for the lost granularity.
Merge branch 'master' into rowcache
Merge branch 'master' of github.com:youtube/vitess
vtgate: add panic handling for public functions