Approximate known const found

[llogiq]

Someone writing 3.1415 should probably use some definition of PI. We should look up other constants in the standard library.

[Manishearth]

+1

[llogiq]

Done. The implementation could be improved (for example, it could return the closest approximation instead of the first found) and the epsilon constant could be changed if we find that we match too much/too little, but it works for me.