failure on shell commands after %%time #11

Hi, thanks for your work!

I encountered the following issue when using this lexer to highlight the contents of a jupyter notebook cell.

%%time
!run_command

This should time the runtime of run_command, but instead it fails on ! because the lexer assumes that whatever comes after %%time should be handled by the normal python lexer.

Reproducing snippet:

from pygments import highlight
from pygments.formatters import TerminalFormatter
from pygments.lexers import get_lexer_by_name

lexer = get_lexer_by_name("ipython3")
code = "%%time\n!cmd"
print(highlight(code, lexer, TerminalFormatter()))