[Fetch] When output is - send to STDOUT

[kylef]

This is so that we can use apiary fetch --output=- to get the blueprint sent to STDOUT.

Required for kylef/apiblueprint.vim#9

[honzajavorek]

Not sure why the Windows build failed. The change seems to be harmless. I'm not experienced in Ruby that much to investigate. Maybe @freaz can take a look?

[freaz]

@kylef Can't you use one of /dev/fd/{0,1,2}?

[abtris]

Maybe you can change output to STDOUT as default without parameters.

[kylef]

@freaz That's right, I'll just use those.

Thanks!