Support IPv6 in address check lookups.

This supports IPv6 in address DNS lookups and socket bind checks. Addresses are
looked up with the system getaddrinfo(), and the v6/v4 preference of this lookup
is respected. IPv6 address literals in the config file are expected to be
bracketed in [], and the result of lookups will be bracketed as well, to support
the ZeroMQ URI format.
Unset the IPV4ONLY socket option if available.

Since IPv6 sockets support both v4 and v6 addresses, the socket option is unset
unconditionally if the parameter is available in the zmq module. The actual
decision as to which address version to use is done by the address lookup code,
which obeys the system v4/v6 preference.
Be more resilient towards missing addresses and hostname lookup failures.
Add a unit test for passing IPv6-formatted addresses to verify_socket.
IPv6 address literals should be specified without brackets in config files.
Clean up some PEP8 stuff
ignore deleted branch in repository
Simplify and fix tests for `salt.modules.hosts`.
We need `OrderedDict` support. So, as a last resort, provide our own.

* We try to import `OrderedDict` from the standard library, which is only available on python >= 2.7, if `ImportError` is raised we try to import it from `ordereddict`, a package available in PyPi. As a last resort, we provide our own implementation based on http://code.activestate.com/recipes/576669/.
* Update all code requiring `OrderDict` to use our compatible import module.
`msgpack` does not like `OrderedDict`'s
Fix the `salt.modules.hosts` tests and even test if order is preserved when writing the new file.
Merge pull request #4575 from sedie-photobucket/develop

fix TypeError with 'remove_groups=False' and 'groups' defined in user.present
Merge pull request #4578 from bclermont/gitfs-deleted-branch

Don't refer to deleted branch in environments list
Also log the sls render exception.
`salt.utils.pydsl.Options` should be a `dict` not an `OrderedDict`.
Add missing CLI example.
Merge pull request #4570 from s0undt3ch/hotfix/fix-travis-again

READ COMMENT: Simplify and fix tests for `salt.modules.hosts`.
Style updates for cmdmod execution module
enable pacman pkg module for Arch ARM
Merge pull request #4581 from mfussenegger/arch-arm

enable pacman pkg module for Arch ARM