Add pending tests

pending function ignores the block passed.
Move pending tests to functional test files
Add Foundation to use NSLog without warning messages
Rearrange functional tests
README: add pending
README: update screenshot
README: explain examples, groups
README: fix indentation for context
s/PoetSpec/DolphinSpec/g
README: use 1st-person in feature descriptions
README: display example right after screenshot
README: add import
README: fix typo s/that/what
README: fix typo expect{}.will
README: add logo
README: explain it better
Highlight the example that failed when an exception is raised
Add functional test for unhandled exceptions thrown in examples

Exposes `-[QuickSpec example:failedWithException:]` as a public method,
and uses it to intercept an exception raised during an example in order
to make assertions on it.
Contain: fix crash for nil failure messages

Unwrapping of optional value in failure message methods caused a crash
to occur when the subject of a failing expectation was nil.

- Remove unwrap
- Spruce up failure message for nil subjects: output "nil" instead of
  "[ nil ]"
Add unit tests for Example._callsite