Enabled testing on HHVM on Travis
Marked HHVM as officially supported
Added the external code coverage for Scrutinizer
Added the scrutinizer badges

[ci skip]
Fixed the composer requirement to allow 1.6
Removed double JS escaping of XPath strings

The XPath query should not be escaped as JS when passing it to the PHP
XPathAccessor of the underlying SahiClient.
This is the result of hacking a fix for multiline XPath in the SahiDriver
without touching the SahiClient, and then fixing it the right way later in
the client.
Fixed the evaluation of scripts
Merge pull request #34 from stof/evaluate_script

Fixed the evaluation of scripts