Links don't work with target="_self"

[antulik]

Description
When the target of a link is set to self, target = "_self", Turbo stops working on that link. Link click does a full page reload.

Steps to reproduce the behavior:
add target = "_self" to link, e.g. <a href="/" target="_self">Click</a>.

Expected behavior
Since "_self" is the default target for a link, it should not trigger a full page reload.

Why explicit _self needed if it's default behaviour?
IF you are using different subdomains, e.g. www.github.com and app.github.com
AND you pinned tab in your browser (e.g. Firefox)
THEN when you navigate across subdomains, the browser will open new tab.
BUT adding explicit target="_self" tells browser to force link in the same tab.

Note
Previously raised issue turbolinks/turbolinks#606