Switched the NameGenerator to a static counter instead of a random suffix
Switched the NameGenerator to a static counter instead of a random suffix

This ensures that the doubler does not generate duplicate class name even
when the generation runs too fast for the entropy source.
Closes #38
Replaces #64 by avoiding to slow down the library artificially because of
md5.

phpspec/prophecy,jakari/prophecy,jakzal/prophecy,ftrrtf/prophecy,kamioftea/prophecy,dantleech/prophecy,Taluu/prophecy