Use the ICLA Signature record for names in table.

A user may or may not have a first and last name in their user record. The ICLA
Signature record for that user should _always_ have a first and last name (as
it is required). This updates the ICLA signers table to use the first and last
name from the signature record instead of the user record.
Merge pull request #613 from opscode/icla_signature_name_in_tables

Use the ICLA Signature record for names in table.