docs: Add migration docs and update readme

BREAKING CHANGE: The verbose option has been removed, as it is now implied by `logLevel` of `DEBUG` or `TRACE`
* All logging and reporting is now on standard out. This was the default before. This means the logDir / format / out options are no longer supported. If your ecosystem needs the ability to customise logging and reporting, please let us know by opening an issue.
* The undocumented option monkeypatch has been removed. The use cases for this feature are mostly covered by other options.
* customProviderHeaders has been removed. Please see the request [filter documentation](https://github.com/pact-foundation/pact-js#modify-requests-prior-to-verification-request-filters) in pact-js.

Author: TimothyJones

MIGRATION.md

@@ -0,0 +1,37 @@
+# Pact-core migration guide
+
+This guide is for migrating code that calls Pact-Core to a new version. 
+If you are a user of pact rather than a maintainer of tools for pact, you
+probably want to be using https://github.com/pact-foundation/pact-js directly
+instead of pact-core. There is a corresponding migration guide there.
+
+# v12.x.x from v11.x.x
+
+## Verifier
+
+* Remove `verbose`. This option has been removed, as it is now implied by `logLevel` 
+  of `DEBUG` or `TRACE`.
+* `customProviderHeaders` has been removed. If you need this functionality, use an 
+  appropriate request filter with `requestFilters` instead.
+* Remove `logDir` / `format` / `out` options, as they are no longer supported.
+
+### Changes you may want to know about:
+
+* All logging and reporting is now on standard out. This was the default before. If 
+  your ecosystem needs the ability to customise logging and reporting, please let us
+  know by opening an issue.
+* The undocumented option `monkeypatch` has been removed. The use cases for this feature are mostly covered by other options.
+
+# v11.x.x. from v10.x.x and below
+
+* Update any calls that recieves a `q.Promise` to simply accept a native ES `Promise`.
+* In `VerifierOptions`: replace use of `tags`, `consumerVersionTag` and
+  `providerVersionTag` with the appropriate `consumerVersionTags` or
+  `providerVersionTags` option.
+
+# v10.12.0 (first version as `pact-core`)
+
+* `@pact-foundation/pact-node` has been renamed to `@pact-foundation/pact-core`.
+  This better describes what it is for, and will hopefully reduce confusion. See
+  [this issue](https://github.com/pact-foundation/pact-js-core/issues/224) for
+  background.

README.md

@@ -303,14 +303,10 @@ pact.verifyPacts({
 | `pactBrokerPassword`        | false     | string  | Password for Pact Broker basic authentication                                                              |
 | `pactBrokerToken`           | false     | string  | Bearer token for Pact Broker authentication                                                              |
 | `publishVerificationResult` | false     | boolean | Publish verification result to Broker (_NOTE_: you should only enable this during CI builds)               |
-| `customProviderHeaders`     | false     | array   | Header(s) to add to provider state set up and pact verification                                            |  | `requests`. eg 'Authorization: Basic cGFjdDpwYWN0'. |
 | `providerVersion`           | false     | string  | Provider version, required to publish verification result to Broker. Optional otherwise.                   |
 | `enablePending`                   | false     | boolean  | Enable the [pending pacts](https://docs.pact.io/pending) feature.       |
 | `timeout`                   | false     | number  | The duration in ms we should wait to confirm verification process was successful. Defaults to 30000.       |
-| `format`                    | false     | string  | What format the verification results are printed in. Options are `json`, `xml`, `progress` and `RspecJunitFormatter` (which is a synonym for `xml`) |
-| `verbose`            | false     | boolean        | Enables verbose output for underlying pact binary. |
-| `logDir`   | false  | string   | Directory to output the pact.log file to
-| `logLevel`    | false     | LogLevel (string)          | Log level. One of "DEBUG", "ERROR", "WARN", "INFO" |
+| `logLevel`    | false     | LogLevel (string)          | Log level. One of "TRACE", "DEBUG", "ERROR", "WARN", "INFO" |
 
 The consumer version selector looks like this: