String diff (or expected/actual) reporting on BinaryExpression

Provide string diff reporting on BinaryExpression such as:

assert(foo === bar)
       |   |   |
       |   |   "abcdff"
       |   false
       "abcdef"

--- [string] bar
+++ [string] foo
@@ -1,6 +1,6 @@
 abcd
-f
+e
 f

Other types:

assert(this.ary.indexOf(who) === two)
            |   |       |    |   |
            |   |       |    |   2
            |   |       |    false
            |   -1      "ariya"
            [1,2,3]

$$$ [number] two
### [number] this.ary.indexOf(who)
$ 2
# -1

Starting with jsondiffpatch but now decided to use google-diff-match-patch directly.

TODO

[x] Searching for nice diff libraries (thx @taichi!)
[x] Detect BinaryExpression left/right
[x] Dealing with Literals
[x] Multibyte characters
[x] Labels and alignments
[x] Multi-hunk diff
[x] Object / Array diff? Or reporter responsibility? -> Reporter's
[x] Only on === and ==
[x] Line level diff
[x] Refactor
[x] Is actual on left and expected on right?
[x] Not only strings?
[x] Update power-assert README since dependencies are changed

power-assert-js / power-assert-formatter

String diff (or expected/actual) reporting on BinaryExpression #4

TODO