Fix issue with FF18.
Added option no-https, to run twisted behind nginx.
Generalize Google verifier to DNS verifier.

Google's Certificate Catalog seems to be defunct. This commit replaces the
Google Verifier with a more gneeric DNS-based verifier. From a user
perspective, one can now provide the DNS hostname of the verifier to use on the
command line, e.g.:

    convergence-notary.py -b dns:your.catalog.here.com

The DNS catalog must accept TXT lookups for hashes, such as:

   1956DC8A7DFB2A5A56934DA09778E3A11023358.your.notary.here.com

Answers should be compatbile to Google Certificate catalog API, i.e., have the
form:

    "x y z"

where

    - x represents the first day the certificate occurred in the catalog
    - y represents the most recent day the certificate has been seen
    - z The number of days in between
Merge remote-tracking branch 'derekelkins/master'