Directory requires unicode paths; add upgrade script from "v0.0.0"

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branch : feature-directory-v1.0.0
Add partitions to directory layer.

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branch : feature-directory-v1.0.0
Change how path is dealt with in DirectoryLayer; add TODOs, fix a couple bugs

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branch : feature-directory-v1.0.0
Fix incorrect use of node.layer()

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branch : feature-directory-v1.0.0
Modify directory to not store path information at the nodes

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branch : feature-directory-v1.0.0
Remove a line previously used for debugging

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branch : feature-directory-v1.0.0
Update API versions (don't sync this branch to Github until after release).

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branch : api-version-200
Update pubsub.py API version

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branch : api-version-200
Initial check in of Rosenthal's RankedSet layer. Updated code for API 200. Replaced in-line Subspace definition with a directory subspace. Updated README accordingly.

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branch : api-version-200
Minor formatting of README.

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branch : api-version-200
Merge from api-version-200