don't require oauthtoken for read commands

[BrainDamage]

currently oauthtoken is required to be set for any command, including passive read commands such as issue listing, etc
it's possible to work around this by setting it as an empty string, afterwards git-hub will still be able to fetch the information, but it shouldn't be necessary to do so

[llucax]

When/if this is done, we have to bear in mind private repos, for which you need a token even for read commands.