Add a Test configuration

This is especially useful for sandboxed apps so they can disable code
signing for tests.
Note that expecta works with XCTest
Merge pull request #98 from andrewsardone/patch-1

[Minor] Note XCTest compatibility in README
Merge pull request #97 from mdiep/test-configuration

Add a Test configuration
fix issue #101
Merge pull request #102 from sspitzer/fix_issue_101

Allow literals in expect invocations