Typo correction

"Flexdevelopers"
Fixing typo "butthere"

This string contains typo:
"Vast majority of today's JavaScript code is being executed by the Web browsers, but thereare JavaScript engines that can execute JavaScript code independently."
Merge pull request #86 from gAmUssA/master

fixing book site build
Merge pull request #84 from TheVasin/patch-1

Fixing typo "butthere"
Merge pull request #45 from slavk0/master

Typo correction
fixing website issue