include shared modules into matchers instead of extend, this is required by rspec 3 and is backwards compatible with rspec 2
remove times parameter from once; once does not use params and this breaks in rspec3
depend on 3.0.0.beta
Remove use of `have` for RSpec3
Fix RSpec 2 and RSpec 3 chain compatibility

We now include the matcher helper, so cannot use `chain`. Instead define the
methods directly and return `self` to chain.
Allow should syntax with RSpec 3
Revert RSpec 3 requirement for now
Update README with RSpec 3 support comments
Update Copyright date
v0.15.0