Notebook with Markdown cell contents are being truncated

[prateek032]

Steps to replicate:

1. Create a new notebook
2. Upload 2 CSV files to it (more than 500Kb)
3. Create a new markdown cell, add some contents to it and execute it
4. Now refresh the tab, Markdown cell becomes 'Text' cell.
   when i open the notebook in GitHub it displays like below

[gordonwoodhull]

Thanks @prateek032

I bet we're not doing language detection properly in the truncation fix-up.