add a class for Dutch names
add a class for Dutch addresses
add a class for Dutch phone numbers

This one might be a bit too realistic. I borrowed the logic from the
French phone numbers.
NL: better api to ask for male and female names
NL: randomize the letters in postal codes
NL: fix some city names
NL: fix some more city names
remove then after else
NL: zip_code is an alias for postal_code
NL: add provinces and tests
NL: add international numbers and tests
NL: add tests for names
NL: remove -Kern from the city names
NL: sort list of cities
Merge pull request #139 from tijn/NL

NL