Fix string quotes bug

[AngelaRemolina]

This PR closes #19
The code is now escaped using JSON.stringify() method.

This PR also does a general maintenance of the Brython module

• A Brython update was needed (from 3.9.4 to 3.9.5)
• Minor style fixes were made:
  • The output just shows when something is printed or there is an error, otherwise it does not.
  • Now, there is a limit to expand the output horizontally
  • The div of errors colors red completely
• A dist folder update was made.