Leave flag.Parse() for go test

[breml]

Fixes #17

[breml]

@matryer can you please have a look at this PR, it just bite my again and I would really appreciate, if this could be fixed.

[breml]

@matryer Could you please have a look at this PR and provide feedback or merge it?

[breml]

@matryer Could you please have a look at this PR, because this bug is pretty annoying for us.

[matryer]

Sorry @breml - does this change anything functionally?

[breml]

@matryer under the assumption, that this library is only ever used for tests (read: in combination with go test), then there is no functional change, because go test does call flag.Parse().
Because in order to use this library one needs a *testing.T, I think it is pretty save to assume, that this library is only used with tests.

[matryer]

Great, thanks.

[breml]

@matryer Thank you very much. Could you please tag a new release such that we can reference it with dep?