gosimple is a Go linter that specializes in simplifying code
Also fix one spelling error in `cred_test.go`
Part of #217
Signed-off-by: Andrew Seigner <siggy@buoyant.io>
In preparation for creating an Identity service that can chain off of an
existing CA, it's necessary to both (1) be able to create an
intermediate CA that can be used by the identity service and (2) be able
to load a CA from existing key material.
This changes the public API of the `tls` package to deal in actual key
types (rather than opaque blobs) and provides a set of helpers that can
be used to convert these credentials between common formats.