updating date time, adding latex tutorial

@etpinard the URL replacements seems weird, but it looks like it works out (in the past this happened to one URL, but this time it looks like the changes are for all of them...). Can you check it out?
@mariahhamel I would remove the `| Plotly Help`. 

Remember `tutorial_name` appears here 
![image](https://cloud.githubusercontent.com/assets/6675409/5170728/096bceaa-73e0-11e4-96a1-98a4c5ddbc1e.png)