PR: Add '+' button to open new notebooks.

[dalthviz]

Fixes #11

[ccordoba12]

This is so nice! Thanks a lot for it.

Is the notebook working well for you on Windows?

[ccordoba12]

Please add a blank line before this one.

[dalthviz]

@ccordoba12 about how the notebook is working:

1. Sometimes Spyder fails to initialice the notebook server at time, so the plugin stays in the load page (Connecting to kernel), so you have to open a new notebook to make it work (I think that maybe this is a problem of synchronization where the notebook server isn't running when the first notebook is trying to run in Spyder).

2. Also if you close Spyder and the cmd where the notebook server is running (the one open by Spyder for the first time), you will have to manually start the notebook server with jupyter notebook command because Spyder doesn't start it again when you reopen Spyder.

3. Also, another problem is the update of the font. When I was trying to change the language a traceback appear:

Traceback (most recent call last):
  File "C:\Users\Daniel\Anaconda3\lib\site-packages\spyder\plugins\configdialog.py", line 218, in button_clicked
    configpage.apply_changes()
  File "C:\Users\Daniel\Anaconda3\lib\site-packages\spyder\plugins\configdialog.py", line 97, in apply_changes
    self.save_to_conf()
  File "C:\Users\Daniel\Anaconda3\lib\site-packages\spyder\plugins\configdialog.py", line 410, in save_to_conf
    self.set_font(font, option)
  File "C:\Users\Daniel\Anaconda3\lib\site-packages\spyder\plugins\configdialog.py", line 985, in set_font
    plugin.update_font()
  File "C:\Users\Daniel\.spyder-py3\plugins\spyder_notebook\notebookplugin.py", line 92, in update_font
    client.set_font(font)
AttributeError: 'NotebookClient' object has no attribute 'set_font'

4. Another traceback appear also when trying to undock the plugin in Spyder 4.0.0.dev0:

Traceback (most recent call last):
  File "C:\Users\Daniel\.spyder-py3\plugins\spyder_notebook\notebookplugin.py", line 131, in refresh_plugin
    self.update_plugin_title.emit()
AttributeError: 'function' object has no attribute 'emit'
Using existing server at C:\Users\Daniel
Traceback (most recent call last):
  File "C:\Users\Daniel\Desktop\Spyder\spyder\spyder\api\plugins.py", line 141, in visibility_changed
    self.refresh_plugin()   # To give focus to the plugin's widget
  File "C:\Users\Daniel\.spyder-py3\plugins\spyder_notebook\notebookplugin.py", line 131, in refresh_plugin
    self.update_plugin_title.emit()
AttributeError: 'function' object has no attribute 'emit'
Traceback (most recent call last):
  File "C:\Users\Daniel\Desktop\Spyder\spyder\spyder\api\plugins.py", line 141, in visibility_changed
    self.refresh_plugin()   # To give focus to the plugin's widget
  File "C:\Users\Daniel\.spyder-py3\plugins\spyder_notebook\notebookplugin.py", line 131, in refresh_plugin
    self.update_plugin_title.emit()
AttributeError: 'function' object has no attribute 'emit'

5. Also a message appears in the notebook pointing an error, however maybe this is normal since the notebook is at first temporal:

[ccordoba12]

About your comments:

1. Please play with the range value below this line:

   /~https://github.com/spyder-ide/spyder-notebook/blob/master/spyder_notebook/utils/nbopen.py#L57

   and submit a PR when you find an appropriate value.

2. We'll fix this in the future, i.e. we'll hide the server cmd window by default. For now, I think it's worth to have it around to check for errors.

3. Fixed in PR PR: Don't try to set the widget fonts for now #17.

4. Fixed in master PR PR: Simplify plugin title #14.

5. I have no idea about that error. We'll have to check it when we meet in person.

[ccordoba12]

@dalthviz, please open an issue about your point 5. so we don't forget to fix it.