public ApnsServiceBuilder withSSLContext(SSLContext sslContext) {
        this.sslContext = sslContext;
        return this;
    }
Specify the SSLContext that should be used to initiate the
connection to Apple Server.

Most clients would use {@link #withCert(InputStream, String)}
or {@link #withCert(String, String)} instead.  But some
clients may need to represent the Keystore in a different
format than supported.

@param sslContext    Context to be used to create secure connections
@return  this
src/main/java/com/notnoop/apns/ApnsServiceBuilder.java