Cloud-files

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* fix(cli): missing part\_bytes argument in a few placs
* test: add CF.get\_json test
* feat: add CloudFile.get\_json
* feat: add --part-bytes to cp CLI
* fixtest: tigerdata -> td

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* redesign: tigerdata.princeton.edu is now td.princeton.edu

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* feat: add reencode to CloudFiles transfer\_to/from
* fix: inverted order of arguments for transfer\_from

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* feat: add transfer\_to/from support for single files
* fix(cli): process matrix://bucket without a trailing slash correctly

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* test: check that clearing and creating locks works
* fix: don't crash if lock dir is None when clearing locks
* docs: how to clear locks
* feat: add lock mechanisms to CloudFile
* redesign: reorganize lock\_dir so that it only tests the fs for file://
* feat: add lock clearing function
* docs: add credit for Ran Lu
* docs: describe how to use local file locking

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* Use fasteners to lock local files (91)
* chore: update changelog
* fix: improper handling of extensions
* fix: zero-length file uploads to GCS don't crash
* Add kwargs to S3Interface (94)