Update be_true and be_false to use new syntax
Switch to Rspec3 style param checking
Uses a constant time string comparison to avoid timing attacks.

Ruby's == string comparison will short circuit once it knows the string is not the same. This could allow a potential attacker to figure out the app secret with a timing attack against the user's webhook endpoint. This uses ActiveSupport's secure compare function to avoid that.
Merge pull request #68 from philnash/fix-timing-attack

Uses a constant time string comparison to avoid timing attacks.
Merge pull request #66 from gocardless/fix-spec-deprecations

Fix spec deprecations
Bump version to 1.11.2