Description:
optional dependencies for notebook should mention python-jinja2 package.

Steps to reproduce:
$ ipython notebook
Traceback (most recent call last):
File "/usr/bin/ipython", line 9, in <module>
load_entry_point('ipython==1.0.0', 'console_scripts', 'ipython3')()
File "/usr/lib/python3.3/site-packages/IPython/__init__.py", line 118, in start_ipython
return launch_new_instance(argv=argv, **kwargs)
File "/usr/lib/python3.3/site-packages/IPython/config/application.py", line 538, in launch_instance
app.initialize(argv)
File "<string>", line 2, in initialize
File "/usr/lib/python3.3/site-packages/IPython/config/application.py", line 89, in catch_config_error
return method(app, *args, **kwargs)
File "/usr/lib/python3.3/site-packages/IPython/terminal/ipapp.py", line 310, in initialize
super(TerminalIPythonApp, self).initialize(argv)
File "<string>", line 2, in initialize
File "/usr/lib/python3.3/site-packages/IPython/config/application.py", line 89, in catch_config_error
return method(app, *args, **kwargs)
File "/usr/lib/python3.3/site-packages/IPython/core/application.py", line 361, in initialize
self.parse_command_line(argv)
File "/usr/lib/python3.3/site-packages/IPython/terminal/ipapp.py", line 305, in parse_command_line
return super(TerminalIPythonApp, self).parse_command_line(argv)
File "<string>", line 2, in parse_command_line
File "/usr/lib/python3.3/site-packages/IPython/config/application.py", line 89, in catch_config_error
return method(app, *args, **kwargs)
File "/usr/lib/python3.3/site-packages/IPython/config/application.py", line 468, in parse_command_line
return self.initialize_subcommand(subc, subargv)
File "<string>", line 2, in initialize_subcommand
File "/usr/lib/python3.3/site-packages/IPython/config/application.py", line 89, in catch_config_error
return method(app, *args, **kwargs)
File "/usr/lib/python3.3/site-packages/IPython/config/application.py", line 400, in initialize_subcommand
subapp = import_item(subapp)
File "/usr/lib/python3.3/site-packages/IPython/utils/importstring.py", line 42, in import_item
module = __import__(package, fromlist=[obj])
File "/usr/lib/python3.3/site-packages/IPython/html/notebookapp.py", line 38, in <module>
from jinja2 import Environment, FileSystemLoader
ImportError: No module named 'jinja2'