Sleep 500ms after using send-keys in tmux.

When creating predefined sessions, add a delay of 500ms so that the
tmux status bar gets updated correctly.
tmux: Ignore refresh-client failures.

tmux refresh-client would fail when there is no active client. This
could happen when trying to run commands using send-keys, and hence is
not a fatal. Also suppress the `no client` warning/error messages.
Add ipython default profile config file.