Set scdl_all_sets from ListSets response
Added docstrings and comments to fetcher.py
Fixed invocation of sed in EDANFetcher.extract_xml_content()

POSIX-compatible sed (like on Darwin, assuming other BSD variants)
requires -e switch for sed code, and the -i option is supposed to
take a string value.  The newline character also needed an extra
backslash-escape.
Removed unreachable function extent_transform() from edan_to_dpla Akara module.

This function is unreachable because the element in the CHO_TRANSFORMER
dictionary that references it is re-defined a few lines down in the same
assignment.
Merge branch 'develop' into type-field-by-format