Set browserstack.local flag for Travis builds

Signed-off-by: Michal Čihař <michal@cihar.com>
Use hardcoded port

Signed-off-by: Michal Čihař <michal@cihar.com>
Set build identifier for local builds

Signed-off-by: Michal Čihař <michal@cihar.com>
Wait for load

Signed-off-by: Michal Čihař <michal@cihar.com>
Enable BrowserStack debugging

Signed-off-by: Michal Čihař <michal@cihar.com>