Updated travis build scripts (from rspec-dev)
Merge pull request #843 from rspec/update-travis-build-scripts-2014-12-17-for-master

Updates from rspec-dev (2014-12-17)
Fix standalone so it doesn’t infect other objects.

This also makes `extend RSpec::Mocks::ExampleMethods`
work properly.

Fixes #845.
Merge pull request #846 from rspec/isolate-standalone

Fix standalone so it doesn’t infect other objects.
Prevent invoked expectations from being modified after they are invoked.
Changelog entry for #837
Use slash line join over array join with spaces
Be less british
Remove empty spec
Remove empty else branch
Improve expectation modification specs
remove redundant block
Use clearer wording for expectation modification message.