[FIX] UnicodeDecodeError 'utf8' codec GZIP

This fixes the problem when compressing after pushing to S3

Implemented based on this comment on the issue:
Details: https://github.com/django-compressor/django-compressor/issues/404#issuecomment-18787650
Oops: Working only on localhost
Allow setup.py develop
Using uncompress gzipped files before using locally
Merge pull request #2 from alanjds/utf-8-fix

[FIX] UnicodeDecodeError 'utf8' codec GZIP