Release expect transformer and browser mode

[skovhus]

Jest is taking over https://www.npmjs.com/package/expect in an upcoming release. As part of this a codemod was developed (#39) and Jest browser support was added for jest-matchers (will be expect@21+) and other relevant packages (jestjs/jest#3360).

Background:

• Expect to jest transformer #39
• Use the "expect" npm package jestjs/jest#1679

Before releasing this:

• Jest release new expect package and document browser support
• revert 8b4bb3f

FYI @cpojer

[SimenB]

jestjs/jest#4345

[skovhus]

@SimenB thanks! We just need to coordinate this a bit with the expect@21 release. Keep me in the loop.

[cpojer]

@skovhus please subscribe to jestjs/jest#4332 also