Added estimation calculation for nth prime number to provide an upper bounds
for the search algorithm. Added hard coded values for the first few primes.
Added tests for the estimation function.
Added the files that were mistakenly not included in previous checkins.
Gem files with semi-stubbed method to generate primes with tests for
the implementation-to-date as well as a prime number estimation method
(and tests for it) that will be used to provide an upper bound for the
prime number search.