Bug: Globalize number formatter is incorrect for numeric digits in supplemental plane

Hi there

globalise (v1.7.0) number formatting is incorrect for cldr-data (v36.0.0), when cldr numeric digits are from the UTF-16 [supplemental plane](https://en.wikipedia.org/wiki/UTF-16#Code_points_from_U+010000_to_U+10FFFF) (from U+010000 to U+10FFFF).

Short example, discussed below: 44.56 formatted in ccp locale
* Should be: "𑄺𑄺.𑄻𑄼" = ["1113a", "1113a", "2e", "1113b", "1113c"] (hex codepoints)
* But returned by globalise: "��.��" = [ 'd804', 'd804', '2e', 'dd38', 'd804' ]

Based on the formatted value returned by globalise, I initially suspected that individual characters are somehow being represented in globalize as surrogate pairs (so two 16-bit hex values), but only the first of these hex values is returned. There's a worked example below, except I now have some doubts over this theory: for the 4 numeric digits involved, 3 of the digits returned by globalize seem to be the first half of a surrogate pair, but one isn't.

**Example (no code)**

For the "ccp" locale, digitals 0-9 are "𑄶𑄷𑄸𑄹𑄺𑄻𑄼𑄽𑄾𑄿", which have unicode hex codepoints of ["11136", "11137", "11138", "11139", "1113a", "1113b", "1113c", "1113d", "1113e", "1113f"].

So the number 44.56 formatted in ccp should be "𑄺𑄺.𑄻𑄼" = ["1113a", "1113a", "2e", "1113b", "1113c"]

What is actually returned from globalise is "��.��" = [ 'd804', 'd804', '2e', 'dd38', 'd804' ]

Using the [Surrogate Pair Calculator](http://www.russellcottrell.com/greek/utilities/SurrogatePairCalculator.htm) for the individual characters in "𑄺𑄺.𑄻𑄼" = ["1113a", "1113a", "2e", "1113b", "1113c"]
* 1113a = **D804** + DD3A
* 1113a = **D804** + DD3A
* 2e = **2e** (no pair needed)
* 1113b = **D804** + DD3B **(but globalise actually returns dd38)**
* 1113c = **D804** + DD3C

So maybe globalise is returning the first hex value from each surrogate pair? But dd38 is returned, not D804 (for 1113b)

**Example (code)**

```
// Output hex values for Javascript unicode characters
var asUnicodePoints = function(value) {
return Array.from(value).map(function(codePoint) {
return codePoint.codePointAt(0).toString(16);
});
};

// For us locale, works fine
var result = Globalize('us').numberFormatter()(44.56);
console.log(result);
=> 44.56
console.log(asUnicodePoints(result));
=> [ '34', '34', '2e', '35', '36' ]

// For cpp locale, wrongly returns first hex value from each surrogate pair?
var result = Globalize('ccp').numberFormatter()(44.56);
console.log(result);
=> ��.��
console.log(asUnicodePoints(result));
=> [ 'd804', 'd804', '2e', 'dd38', 'd804' ]

// For ccp locale, the true hex values for formatted 44.56 should be..
console.log(asUnicodePoints("𑄺𑄺.𑄻𑄼"));
=> [ '1113a', '1113a', '2e', '1113b', '1113c' ]
```