Motivation:
Sometimes it's easier to get keys/certificates as `InputStream`s than it is to
get an actual `File`. This is especially true when operating in a container
environment and `getResourceAsInputStream` is the best way to load resources
packaged with an application.
Modifications:
- Add read-from-`InputStream` methods to `PemReader`
- Allow `SslContext` to get keys/certificates from `InputStreams`
- Add `InputStream`-based setters for key/trust managers to `SslContextBuilder`
Result:
Callers may pass an `InputStream` instead of a `File` to `SslContextBuilder`.