Rename be_true and be_false to be_truthy and be_falsey.

Signed-off-by: Sam Phippen <samphippen@googlemail.com>
Merge branch 'change-be-true-false-to-truthy-falsey' of https://github.com/samphippen/rspec-expectations into change-be-true-false-to-truthy-falsey
Alias be_falsy to be_falsey.

Signed-off-by: Sam Phippen <samphippen@googlemail.com>
Merge pull request #284 from samphippen/change-be-true-false-to-truthy-falsey

Rename be_true and be_false to be_truthy and be_falsey.