implement streaming responses
various cleanups
pumpStreamOnce -> pumpStreamInternal
pass an Error to reject(), and reject in the unknown case too
Merge pull request #81 from dwrensha/streaming

implement streaming responses ♫♫
Merge pull request #85 from jparyani/grain-links

Allow linking to locations within grains
Actually, let's just have the postMessage format be {'setPath': '/whatever'}.
Merge pull request #88 from jparyani/grain-links

Fix error reporting for invalid paths
Fix grainLog route from conflicting with grain path. Fixes #99