Fixing some css minors in full_html and reveal.
Merge pull request #3690 from damianavila/fix_css_html

Fixing some css minors in full_html and reveal.

There are some issues in the padding of pre tag making the cell bigger and with lot of space around the text in the full_html template, so I put a reasonable padding to fit the cell in a proper way...
And I have also aligned the output prompt with the imput prompt in the reveal template.