Merge pull request #9 from bcail/develop

add ID attribute to root mods element
whitespace/linter cleanup
correct path for changelog inclusion in sphinx docs
update eadmap with support for digital archival object tag (dao)
add entry to changelog about mods id attribute contributed by bcail
try alternate squid startup to see if it helps xsd timeout on travis-ci
run travis-ci tests without squid/http proxy
declare xlink namespace in a way that makes it easier to re-use
restore pip dev requirements file for generating documentation on readthedocs.org