Add coverage for fuel-* scripts

[lamblin]

Scripts like fuel-download used to be outside of the fuel package, and not tested for coverage. Now, we need them to be importable, so #211 moved them to fuel.bin, and made coveralls ignore them. We should add tests in nose that call the various fuel.bin.*.main() functions, or find a way to make coveralls consider the calls to fuel-download as part of the coverage.