[Fix]: Diff viewer(#1229, #1132, ...)

[a8m]

This PR should fix some issues in the Diff viewer that depends on the stringify function
for example:

• Diff Viewer Verbosity with -0 #1229:

expect(-0).eql(0);  // assert with empty representation
expect({ n: -0 }).eql({ n: 0 });  // same with the canonical behavior
expect(-0).eql(1);
/* representation:
  +expected: 1
  -actual: 0

• buffer diff Diffs for buffers #1132 :

expect(new Buffer([0x01])).eql(new Buffer([0x02])); // asset with empty representation

• Infinity,NaN:

expect({ infi: Infinity, nan: NaN }).eql({});
/* representation:
-{
-  "infi": null
-  "nan": null
-}
this happens because JSON.stringify(NaN/Infinity) returns `null`(could fixed with `replacer` function)

• Date, RegExp, Function and Circular represents as a string:

var actual = {
  string: "string",
  regex: /^[a-z]/,
  func: function() {},
  date: new Date(0)
};
actual.circular =  actual;
expect(actual).eql({});
/* should represent without the `"` sign(that indicating to string representation)
 -{
 -  "circular": "[Circular]"
 -  "date": "[Date: 1970-01-01T00:00:00.000Z]"
 -  "func": "[Function]"
 -  "regex": "/^[a-z]/"
 -  "string": "string"
 -}

- This PR fixed that and the result will be like so:
 -{
 -  "circular": [Circular]
 -  "date": [Date: 1970-01-01T00:00:00.000Z]
 -  "func": [Function]
 -  "regex": /^[a-z]/
 -  "string": "string"
 -}

I changed the current specs, created more tests to get full coverage and did some DRY refactoring

[travisjeffery]

broken tests?

[a8m]

@travisjeffery the tests was failed on 0.8 and 0.11 versions, I fixed that in fea3fb7ad291d8fad0b5d0edc6fced987b24e579
thanks

[a8m]

//cc @boneskull

[travisjeffery]

@a8m can you squash these commits? thanks

[a8m]

@travisjeffery done.
thanks

[a8m]

Awesome @travisjeffery
Thx