Using pdftex and Roboto package

[rougier]

Following issue #23, I think it should be possible to used pdftex only since there exists a Roboto package and a source code pro.

It is a matter of modifying the rescience.cls whcih already contains commented code for PDFtex but then I get lost in specifying the right shape and weights for section and title.

Also, for the nalme of the journal, we need to enlarge tracking which can be done with the microtype package.

If someone want to try, that would be helpful and we could get rid of the local fonts.