Number spelling based on the CLDR's RBNF rules

A pure Python engine for parsing RBNF rules.
The rules are incomplete in many cases, fractional
number spelling is hardly supported.

Based on an earlier discussion:
#114
and referenced in
#179

babel/numbers.py

@@ -24,6 +24,7 @@
 import warnings
 
 from babel.core import default_locale, Locale, get_global
+from babel.rbnf import RuleBasedNumberFormat
 
 try:
     # Python 2
@@ -662,6 +663,26 @@ def __init__(self, message, suggestions=None):
         self.suggestions = suggestions
 
 
+def spell_number(number, locale=LC_NUMERIC, **kwargs):
+    """Return value spelled out for a specific locale
+    
+    :param number: the number to format
+    :param locale: the `Locale` object or locale identifier
+    :param kwargs: optional locale specific parameters
+    """
+    speller = RuleBasedNumberFormat.negotiate(locale)
+    return speller.format(number, **kwargs)
+
+
+def get_rbnf_rules(locale=LC_NUMERIC):
+    """Return all the available public rules for a specific locale
+
+    :param locale: the `Locale` object or locale identifier
+    """
+    speller = RuleBasedNumberFormat.negotiate(locale)
+    return speller.available_rulesets
+
+
 def parse_number(string, locale=LC_NUMERIC):
     """Parse localized number string into an integer.