Disable certificate-transparency-go integration tests

[codingllama]

Temporary until certificate-transparency-go vendors its dependencies, at
which point Travis should work again

[Martin2112]

Possibly not much point waiting for the tests.

[codingllama]

Tests should be green, otherwise the fix failed. :)

Feel free to merge before me if I take too long.

[codecov-io]

Codecov Report

Merging #822 into master will increase coverage by 10.21%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           master     #822       +/-   ##
===========================================
+ Coverage   53.47%   63.69%   +10.21%     
===========================================
  Files           7       92       +85     
  Lines         374     7037     +6663     
===========================================
+ Hits          200     4482     +4282     
- Misses        156     2156     +2000     
- Partials       18      399      +381

Impacted Files	Coverage Δ
trillian/testdata/signer.go
trillian/ctfe/handlers.go
trillian/util/timesource.go
asn1/common.go
jsonclient/client.go
types.go
signatures.go
docs/storage/commit_log/simkafka/kafka.go	84.78% <0%> (ø)
storage/mysql/admin_storage.go	73.92% <0%> (ø)
quota/kind_string.go	50% <0%> (ø)
... and 89 more

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