explicitly install kexec-tools on all platforms

on trusty, kexec-tools is no longer a dependency of linux-crashdump. We
now install it explicitly to make sure we have the `kdump` service, so
we can actually *load* the crashkernel.

n.b.: we cannot test for service enabled because beaker-puppet checks
for runlevel 3, and kdump starts in 2.

This commit fixes #2
update Gemfile, Rakefile and spec from puppet-module-skeleton

This also removes our version parsing code, because
puppet-module-skeleton contains code to deal with that.

    % rake module:release

now does all the things, and I didn't need to write code for it.
[blacksmith] Bump version
[blacksmith] Bump version