Stop supporting invalid YAML

domains:
  - *.domain.com

is not valid in Psych, which is the only parser supported in jruby 1.7.

Instead, valid syntax is:

domains:
  - "*.domain.com"
Don't depend on thin which doesn't work on jruby
jruby compatibility
Display error when Cloudfile has invalid YAML

[#41581539]
Remove dependency on grit [#41346975]
Enable jruby builds on travis
1.8 compatibility