tests: added downloader middleware manager integration tests for gzipped redirection.
Split redirection into status and metarefresh middlewares, also changes httpcompression priority. closes #78
update DOWNLOADER_MIDDLEWARES_BASE setting documentation
Add MetaRefreshMiddleware docs
update metarefresh settings
pep8ize settings
add meta-refresh changes to release notes
TakeFirst doc says it returns first non-null/non-empty value, zero is a valid value. closes #59