Make BAI indexing work again

When you pass pywebhdfs's [create_file](http://pythonhosted.org/pywebhdfs/#pywebhdfs.webhdfs.PyWebHdfsClient.create_file) something other than a string, it quietly URL encodes it. This meant that `$.getJSON` was failing to load these files as JSON. We assumed that a failure of `$.getJSON` was due to a non-existent file, rather than some other reason, and swallowed the error. So we never noticed (except via slower page loads).

I tested this fix by running the indexer manually on my workstation.

Fixes #397 

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