Use IPy for IP check

While socket.inet_aton does correctly identify addresses it can return
very unexpected results such as '123.123123' being interpreted as
'123.1.224.243'. This causes issues because IPy won't interpret
'123.123123' as an IPv4 address at all.

Switching to IPy for determining if something is an IPv4 or IPv6 address
fixes this. Downside/bug/feature being that '123.123123' won't be
interpreted as an IP address at all.

Fixes #453.
Merge branch '453-ip-check'
Update VRF info from parent prefix

When adding a prefix from another prefix the VRF info is now fetched
from the prefix we are allocating from.

Fixes #386.
Merge branch '386-fix-add-prefix-vrf'
Build artifact collection for Pylint to Amazon S3

This introduces build artifact collection to Amazon S3 storage as well
as the actually running pylint on nipap, pynipap and nipap-cli to get
some real data to store :)

Pylint data is only collected for the master branch.

Part of #274.
Merge branch 'build-artifacts'
Whops, fix pylint

Accidentally changed .travis.yml last minute which broke the upload of
build artifacts :(
Add timestamp to pylint files

.. which will make it a lot easier parsing them afterwards and turning
them into a nice graph over time.

Part of #274.
Improve nipap-cli handling of default_vrf

The configuration option 'default_vrf' has now been replaced with two
new ones;
 - 'default_vrf_rt' only affects address adds/edits/removals and in
   which VRF to search when adding a member prefix to a pool for the
   first time - if the pool already has member prefixes, the implied VRF
   of the pool will be used.
 - 'default_list_vrf_rt' control the default VRF for listing/search
   operations, ie 'nipap address list'.

The output of VRF related information has been changed for all commands
to include both the VRF RT as well as the name. All search strings and
similar are now enclosed in single quotes when used in various messages
to make it clear what is a pool name and what is just part of the
message.

Some logic around handling the global VRF has been removed since there
is always a VRF (change made quite long ago actually).

Part of #451.
Fixes #386.
Merge branch '451-default_vrf'
Fix listing of stuff in CLI

Fix logic to avoid print "No matching ... found" when number of result
fall on limit. Ie, 50 prefixes would pring "No matching prefixes found"
as the limit is set to 50.

Fixes #461.
Add column headers to address list

This adds column headers as well as a message showing which VRF we are
searching in.

Fixes #463.
Merge branch '461-listing-fix'