jest 20.0.1

• Add ansi-regex to pretty-format dependencies (#3498)
• Fix <rootDir> replacement in testMatch and moduleDirectories (#3538)
• Fix expect.hasAssertions() to throw when passed arguments (#3526)
• Fix stack traces without proper error messages (#3513)
• Fix support for custom extensions through haste packages (#3537)
• Fix test contexts between test functions (#3506)