Moved database related files to ct/client/db.
Merge pull request #311 from phad/master

Add Paul Hadfield to CONTRIBUTORS
TLD checks for common names and dnsnames.
Multiprocess parsing of der_certs.
High tags implementation.
Reporter -> TextReporter, AggregatedReporter
Consumer won't overflow reporters.
Check subject common name None.
Not all details can be casted to str.
Store certificates in CertDB.
Log precisely which certificate blew up scanning
Parse certificate version correctly.