Make symmetric_secret optional in ccng template

This is no longer a required property in ccng.
Moreover, its absence is used to indicate that the
UAA is using an asymmetric signature for tokens so
it has to be optional in the yaml template.
Merge pull request #59 from tekul/feature/ccngsecret

Make symmetric_secret optional in ccng template
Bump dea

dea shortlog 2ca4fcd..e7db702
Jesse Zhang (1):
      Remove broad rescue [#46751287]

Maria Shaldibina and Max Brunsfeld (3):
      Reorganize buildpack fixtures
      Compute reserved memory and disk correctly in ResourceManager
      Support memory and disk overcommit factors [#46311945]
Postgres startup timeout typo fixed
Bump CCNG

git shortlog 1e37c0..a6dff3
Alex Suraci & Bleicke (1):
      Remove a broad rescue [#46751287]

David Sabeti and Tony Hansmann (1):
      Make sqlite3 production dependency in Gemfile

Dmitriy Kalinin and Mark Rushakoff (10):
      upgrade sequel
      monkey patch sequel with class_evals instead of reopening classes
      remove fk constraints before dropping columns for mysql
      make sequel happier
      fix querying by boolean api when using mysql db
      make sure that apps cannot have same name in different case
      fix tests when running with postgres
      add postgres and mysql travis build jobs
      mention DB_CONNECTION env variable for testing
      wrap README to 80 chars
Allow UAA URL to be optionally specified in manifest