fixed python files in firefox (ignore "; charset=UTF-8" in firefox)

Fixed issue that the editor cannot recognise python file because the
content type “text/x-python; charset=UTF-8” has “; charset=UTF-8”.
There was no syntax highlighting and execute button because of it. now
it fixed.
Merge pull request #73 from Leon-G/master

fixed python files in firefox (ignore "; charset=UTF-8" in firefox)