Get the actually used cipher name,bits,version of the established
connection.

get_cipher_name, get_cipher_bits, get_cipher_version methods are
wrappers for SSL_get_cipher_name, SSL_get_cipher_bits,
SSL_get_cipher_version

https://www.openssl.org/docs/ssl/SSL_get_current_cipher.html
https://www.openssl.org/docs/ssl/SSL_CIPHER_get_name.html
Test methods test_get_cipher_* have been split into two sets.
assertTrue(isinstance was replaced with assertIsInstance.
assertEqual for None was replaced with assertIs.
Added entries to doc/api/ssl.rst.
Replace assertIs with assertTrue,
because assertIs is not supported in Python 2.6
whitespace: three blank lines between top-level suites, two blank lines between indented suites
Add return type API documentation.
ChangeLog entry
merge master
Use assertIdentical instead of the other thing.
Return unicode from these new APIs rather than the native string type.
Merge pull request #83 from exarkun/current_cipher_info3

Introduce Connection.get_cipher_name, Connection.get_cipher_bits, and Connection.get_cipher_version.