Add scrutinizer badges to README.

Also removes the unstable build badge, which is kind of redundant since
we will always respect the pattern of keeping the `master` branch stable
enough to be used.

Two Scrutinizer badges were added: code coverage and code quality.

Travis changed to report code coverage to Scrutinizer.
Removes new line from beggining of file.

Since this is considered output by PHP and could harm the output buffer
for requests that will send headers after this.

Nasty bug.
Merge pull request #193 from augustohp/189-scrutinizer

Scrutinizer code coverage and custom Makefile support
PSR-4