Better failure when screenshot doesn't save

* Non-writable paths would raise JSON::ParseError
* Now a clearer error is raised
Correct link for reporting crashes

* Link previously referenced Stack Overflow.
* We have a page for this in the wiki.
* Updates the link to reference the wiki.
This fixes a stderr redirection test on fast machines. The write pipe was
getting closed before the redirection thread had a chance to copy it's
contents into it.
Qt 5 moved to ubuntu-sdk-team PPA

* Fixes build issues on Travis
Ignore .idea directory
Bump selenium-webdriver dependency