Updated crypto-random to 1.2.0
Updated bcrypt work factor to 11

This takes ~200ms on a AWS t1.micro instance, which is approximately
the same time as the PBKDF2 algorithm takes with its defaults.
Updated scrypt CPU cost to 2^15

This takes ~150ms on a AWS t1.micro instance, which is approximately
the same as the time the PBKDF2 and bcrypt algorithms take with their
defaults.
Updated README with explanation of iteration defaults