Import initializeEach() from causes.git

In causes.git we use initializeEach() to squeeze more value out of
replace.js. This commit imports initializeEach() into replace.js so that
others can benefit from the functionality. This is a straight move with
no modifications; it corresponds to initializeEach as it existed at the
current HEAD of the master branch in causes.git (commit
84912bc74c3046887b4).

A subsequent commit will do the same for our "data-lazy-url"
functionality, and at that point we'll be able to look at making
ajaxReplace an internal-only function (this will require some work on
the Causes side).

Related issue:
  https://github.com/causes/replacejs/issues/2
  ("Move lazy-load functionality into replacejs repo")

Change-Id: I18126382149f30c2917b527a03bafe0443d10db8
Reviewed-on: https://gerrit.causes.com/25809
Reviewed-by: Joe Lencioni <joe.lencioni@causes.com>
Tested-by: Greg Hurrell <greg@causes.com>
Import "data-lazy-url" functionality from causes.git

Much as we did in the last commit, here we're bringing across useful
functionality from causes.git (corresponding to commit
84912bc74c3046887b4 of the master branch); this time it is our
"data-lazy-url" functionality.

This is a straight move, and brings with it a dependency on the jQuery
waypoints plug-in:

  http://imakewebthings.com/jquery-waypoints/

In a subsequent commit, I'll turn this into a soft dependency (ie. the
behavior should degrade gracefully in the absence of the plug-in), but
for this initial commit I wanted this to be a clear-cut move operation
with no modifications.

Related issue:
  https://github.com/causes/replacejs/issues/2
  ("Move lazy-load functionality into replacejs repo")

Change-Id: Ia1a0e5213c7b6ec51ce08f4986b03f0815beb1df
Reviewed-on: https://gerrit.causes.com/25810
Reviewed-by: Joe Lencioni <joe.lencioni@causes.com>
Tested-by: Greg Hurrell <greg@causes.com>