Python HFile Reader (#3290)
Python HFile Reader (#3290)

* Create HFile reader which can read Trailer and raw DataIndex

* Test scalding job for thrift decompression eval

* Add ability to read Index and Meta blocks

* Read raw data blocks robustly

* Make blocks single-readable

* Update index decoding to parse varints.

* Add note about block size upper limit.

* Git rebase got weird.

* PEP 8 fixes.

* Clean up code and remove test Scalding job.

* Response to reviewer feedback.

(sapling split of f12e04c43ce917661dc5db51b74d5caf5e8b23c0)

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