Start dynamic layers work in branch
Merge branch 'master' into dynamic-layers
Merge branch 'master' into dynamic-layers
Fix tests, finish work here. Needs a design hit.
Update make for tests
Extract Relation#replaceMember
A no-op Graph#replace should not create a new graph

This is useful for reducing graph churn.
Set up iD.actions.Join to be more flexible
Support merging points into an area (#435)
Move common setup to spec_helpers.js
Remove more unreliable or slow layers, select the right layer initially,

fix null tooltips
Join should run Reverse where necessary (fixes #652)
Fix sourcetag regression
Merge branch 'master' into dynamic-layers

Conflicts:
	js/id/renderer/background_source.js
	js/id/ui/layerswitcher.js
Merge pull request #665 from systemed/dynamic-layers

Dynamic layers
Fix snapping nodes to areas

In the future it may be good to use shadow paths, but at this point
there isn't really a reason to add thousands of additional paths.
Remove unscoped d3.select
Switch back to mouseup, and block following click
Improvements to Split

* Split a closed way at selected and antipode point (fixes #651)
* Split an area into a multipolygon (fixes #572)
Fix add_point tests (switch back to mouseup)