Crashes if .i3agenda dir doesn't exist when trying to read pickle file

[Tomer Rosenfeld]

We get a file not found error because the CONF_DIR doesn't exist

This line

i3-agenda/i3_agenda/API.py

Line 47 in ef5668a

 with open(TMP_TOKEN, "wb") as token: 

If the path doesn't exist, it should be created (mkdir $CONF_DIR)