Bug fix: correctly persist cassette path

Thanks Alexandre for his PR!

Introduced support for binary body

Thanks to Richard for his PR.

Update to README

v2.1.0

Update README.md

Streamlined FilterFuncs

This release changes the API and hence is tagged as v2.

It removes the v1 style FilterFuncs and consolidates them in two new FilterFuncs: RequestFilterFunc and ResponseFilterFunc.

RequestFilterFunc receives the request Header / Body to allow their transformation. Both the live request and the replayed request are filtered at comparison time. Transformations are not persisted and only for the purpose of influencing comparison.

ResponseFilterFunc is the flip side of RequestFilterFunc. It receives the response Header / Body to allow their transformation. Unlike RequestFilterFunc, this influences the response returned from the request to the client. The request header is also passed to ResponseFilterFunc but read-only and solely for the purpose of extracting request data for situations where it is needed to transform the Response.

Fixes and improvements

Patch a silly bug with the default ExcludeHeaderFunc.
Some improvements.

Added support for custom cassettte location

Via VCRConfig.CassettePath

Quick example:

    vcr := govcr.NewVCR("MyCassette",
        &govcr.VCRConfig{
            CassettePath: "./govcr-fixtures",
        })

Note:
If you omit CassettePath or use "" then the default path is ./govcr-fixtures.

First stable fully functional release

This is the first stable release.
All functionality is implemented as per documentation.