Make Egyptian fractions a little more robust.

Add checking for negative arguments, and arguments > 1
Add check for legal input in egyptian fraction.

Reject numbers outside of (0,1), instead of trying to handle them.
Add Golomb's method for Egyptian fractions.
Use harmonic method for Egyptian fractions

Sum divergent series for values > 1.
Merge pull request #7573 from clsn/egyptians

Make Egyptian fractions a little more robust.