diff improvements

[brodieG]

Word diff not working fantastic in these cases:

@@ .ref @@
-  [1] "**`1:3` should** be length 5 (is 3)"
@@ .new @@
+  [1] "**should** be length 5 (is 3)"

** added for emphasis since colors not shown. should should not be part of the diff.

[brodieG]

Do we need a version of all.equal like alike that returns the index difference?

• could save expression to history so all user has to do is hit up and have the object with subsetting expression read to go
• Need to reconcile issues with first actual diff possibly not being first display diff and ending up really confusing situation where visual diff is showing one error, but the value diff is showing another

[brodieG]

This is resolved with integration with diffobj