docker-api v1.32 dropped support for Ruby 1.9

[ianbamforth]

No longer possible to install this with Ruby 1.9, as https://github.com/swipely/docker-api/releases/tag/v1.32.0 dropped support for 1.9. Setting <1.32 in the synapse.gemspec appears to resolve this.

[jolynch]

@ianbamforth can you just install docker-api manually before you install synapse?

e.g.

gem install docker-api -v ...
gem install synapse