Add basic Functions.

Add spherical and sigmoid functions (migrated from cilib/scala).
Add license and contributors information.

Add BSD3 license file with copyright. Add CONTRIBUTORS file.
Merge pull request #2 from avanwyk/functions

Add basic Functions.
Correct generator test case

Signed-off-by: Gary Pamparà <gpampara@gmail.com>
Simplify fitness code.

Rather use an applicative functor to make the fitness decisions. This
greatly simplifies the logic.

Signed-off-by: Gary Pamparà <gpampara@gmail.com>