* support for 'classic' pywb features and misc improvements:
- add support for redirect to exact timestamp mode via 'redirect_to_exact: true' config setting
- tests: ensure memento headers added for redirect-to-exact
- memento: ensure Link header added for intermediate resources, check for 'enable_memento' before adding
- config: config passed to head_insert template as 'config'
- insert legacy 'vidrw.js' script if 'enable_flash_video_rewrite' config is set to true
- config: use_js_obj_proxy now defaults to true
- memento/tests: add proxy with custom accept-datetime test
