Modified siRNA design rules by Ui-Tei and Reynolds

 * Ui-Tei rule: Avoided contiguous GCs 10 nt or more.
 * Reynolds rule: Total score of eight criteria is calculated.
   * Returns numerical score for functional siRNA instead of returning 'true'.
   * Returns 'false' for non-functional siRNA, as usual.
 * Unit tests are modified to reflect these changes.