Converted to the new RSpec syntax

* Using `rspec-its` to keep the old `its` feature
* truthy and falsey instead of true and false in expectations
* Convert `pending` to `skip`
* Renamed ill-named example variable to example-document
Unify usage of `and_return`

Don't use the block syntax if lazy execution is not necessary.
Merge pull request #94 from triAGENS/rspec-deprecations

Look  through RSpec Deprecation Warnings