Performance improvements

With these changes, a real-world script to parse 50,000 phone numbers went from
taking 150 seconds on my machine down to 100 seconds, i.e. about 50% speed
increase.
Changes phone_data array to a hash

Change makes it possible to use direct Hash lookups instead of Array.find to get
the relevant country's data, which is quicker for lookup.
Merge pull request #23 from HerbCSO/improve-performance

Performance improvements