Merge pull request #2 from GraceNut/does-codecademy-teach-python3

fixed typo.  'suddle' to 'subtle'
update so all references to "Python 3" are "Python3"
Merge branch 'does-codecademy-teach-python3' of github.com:sharocko/help.codecademy.com into does-codecademy-teach-python3