Speed up Travis CI

> Travis CI should now show the commands that build.sh executes in the
> log. I mean commands, not only their output.

I should probably remove this part, shouldn't I? It seems that there is already more beautiful way to show what is happening.

The first job time dropped from `6 min 33 sec` to `2 min 4 sec`.

<hr/>

commit b1b5a3eac90c079f4f9ebb909654d4c9c89fd915
Author: Mikaela Suomalainen <mikaela.suomalainen@outlook.com>
Date:   Sat Aug 2 18:44:01 2014 +0300

    tests: make build.sh show executed commands & ...
    
    ...try to speed up make by using multiple jobs if there is more than one
    CPU available
    
    Travis CI should now show the commands that build.sh executes in the
    log. I mean commands, not only their output.

commit 21538edc9b822990aa62734664be051dea1ae687
Author: Mikaela Suomalainen <mikaela.suomalainen@outlook.com>
Date:   Sat Aug 2 18:39:39 2014 +0300

    core: enable fast_finishing (Travis CI)
    
    fash_finish makes it so that if one job fails, the build is marked as
    failed without having to wait for the other jobs to finish. If there are
    still unfinished jobs at the time of failure, they continue running
    after the build has been marked as failed.