Fix GPG key error

[xhdix]

Close #58

[anadahz]

The Travis build errors due to GPG key issue, see pull request: #57

[xhdix]

@anadahz Can you verify the changes?

[anadahz]

@xhdix I guess it's better to revert your changes.
Pull request (#57) is approved and should be merged soon.

[xhdix]

@anadahz OK, I have reverted the changes to the .travis.yml file.
Three other files still need to be modified. I'm not sure about the changes to the file scripts/setup-dependencies.sh.

[anadahz]

@xhdix #57 is merged. You can rebase your branch to the current master to resolve Travis errors.

[xhdix]

I think everything is right now.
@hellais @bassosimone please review.

(I made the changes with the Atom editor so the extra spaces are automatically deleted)

[hellais]

LGTM