bump version to 0.6.6
rewrite: add per-collection rewrite options, settable in 'rewrite_opts'
block in each collection. Added rewrite_base to disable rewriting <base>
tag and rewrite_rel_canon to disable rewriting link rel=canon.

Disabling <base> tag rewrite fixex #51 and new system addresses #50 as
well.
Fix quotes in CHANGES.rst
rewrite: refactor JS rewriters into seperate mixins, allowing for
link only, location only, and link + location JS rewriters.
location-only rewriter is new
js_rewrite_location options: all, location, urls (for now)
update changelist
wb js: add guard around wb js to prevent double-inits (such as from
fragments!)
wb.js: don't include anchor when comparing current url with expected top
url
wb.js: preserve anchor in location redirect
update CHANGELIST
Merge branch 'develop'