Test that links with unknown schemes are removed
Allow customization of allowed <a href> URL schemes

A new context parameter, :anchor_schemes, can be used to override the
default list of allowed schemes.

Note that this means that these schemes are no longer configurable via
the :whitelist context parameter. They can only be controlled via
:anchor_schemes.
Merge remote-tracking branch 'upstream/master' into configurable-schemes-bug-fix
Safely dup protocols by providing default hash
Put the default anchor schemes back in the default whitelist

Clients of this gem may have been relying on this.
Add a test for SanitizationFilter::ANCHOR_SCHEMES

Clients may come to rely on this, so we should have a test to ensure we
don't break them.
Allow specifying anchor schemes in the whitelist itself

If context[:anchor_schemes] is not passed, we use the schemes that are
specified in the whitelist itself. This matches our behavior from before
:anchor_schemes was added.

If :anchor_schemes is passed, it overrides any schemes specified in the
whitelist.
Merge pull request #98 from aroben/configurable-schemes

Allow customization of allowed <a href> URL schemes