If we want to build other projects (kiwix-lib, kiwix-tools) with travis,
it is better to have all dependencies already compiled.
kiwix-build project now compiles them and publishes the dependencies
archive at the right place where other projects can use them.
Make `kiwix-build.py` also fail if sub-command fail instead of just print
an error message and quit.
`kiwix-deploy.py` is far more simple and already fails miserably if a
sub-command fails.
Matthieu Gautier