Change private key order to prefer RSA oder DSA

RSA is more secure, due to longer cipher lengths.
1024bit (DSA default) should not be used anymore.
Add Ed25519 to private key list
Update HostKey, HMAC and Kex ciphers

Add ciphers recently added to openssh (since openssh-6.4)
Adapt test for new ciphers #1

test_constructor_should_build_default_list_of_preferred_algorithms
Adapt test for new ciphers #2
Update chipers for known_hosts

Add ciphers recently added to openssh (since openssh-6.4)
Adapt test for new ciphers #3
Merge pull request #160 from chr4/new-ciphers

New ciphers