Update the Gemfile to look similar to what is currently recommended
for cross-platform development by Puppet Labs.

 - Having it as a tag reduces the score on puppet forge because it
conflicts with `$::operatingsystem` fact -
https://docs.puppetlabs.com/puppet/latest/reference/modules_publishing.html#fields-in-metadatajson

Travis-Lint has been deprecated and the linting aspect has been taken
over by the `lint` function in the travis gem.
https://github.com/travis-ci/travis-lint#what-is-travis-lint

Allow running rake tasks without issues.

Now the specs pass again on both Windows and *nix. The switchover to
checking for the existence of a file and the reorder of how choco
searches for the binary made the tests start failing.

Build Enhancements

When ensure => $version, the underlying package provider will call
install instead of upgrade if the package is already installed.
Chocolatey's default install behavior is to do nothing if a package is
already installed, even if there is a newer version available. In most
cases we can call upgrade, except when the installer is using a
packages.config.

We'll also need to address the use of side by side installs, which this
will remove the ability to do.

(GH-71) Use upgrade instead of install