remove conditional apt-get udpate

COOK-2171 was resolved and released in Junary 2013, and there's been
many releases to the apt cookbook since then. No need to incude this
extra apt-get call during each Chef run.
doc update
remove conditional python dep for Ubuntu 11.04

11.04 has been EOL since 2012-10-28
https://lists.ubuntu.com/archives/ubuntu-announce/2012-October/000165.html
update repository recipe to choose correct arch

- yum repo now requires a switch based on architecture, map each value to
the correct path and select a default of 64-bit.
- apt repo now contains a `stable` distribution, which can be switched
  via attribute
adapt logic in agent installer to work with 5.x

With datadog-agent 5.x and higher, there is no logner a need for the
`base` package on any platform, there's only some requirements around
using the correct package on the right platform.

This changes both the logic itself as well as the testing suite for
versions.
remove support for chef handler logic magic

This was only to support Chef versions prior to 0.10.9 - this version is
far gone, and the method is generally simpler.
remove any integration-specific dependencies

These are no logner needed from version 5.x and higher.
replace tailor with rubocop
whitespace removal
update deprecated method call, styling
address StringLiterals [style]
update to testing

Gemfile updates, which versions to test on
update for some kitchen box urls
chef-datadog, 2.0.0