add a "tabs" implementation

Put each UIWebView on a main horizonally-scrollable UIScrollView
next to each other.  When hitting the tabs button, zoom out on each
one and allow paging through them.

Bind URL requests to each WebViewTab.

Still needs work to make a "context" toolbar when zoomed out to add
a "+" button, and to detect javascript window.open and <a
target="_blank"> to open in a new tab.
update README with tabs progress
add a URL blocker to stop tracking devices

Ghostery's ruleset is under strict terms, so it can't be used:
https://cdn.ghostery.com/update/all

Disconnect's is under GPL 3 which would taint everything, so that
can't be used either:
https://raw.githubusercontent.com/disconnectme/disconnect/master/firefox/content/disconnect.safariextension/opera/chrome/data/services.json

Unfortunately this means the tracker list is going to have to be
built new, from scratch, basically duplicating all of the effort of
Ghostery and Disconnect :(

While here, move some resources into a Resources directory
README: we have a url blocker now

unfortunately it's not ghostery or disconnect's