(#190) Fix file expansion crash when $HOME is not set.

Without this patch, when facter is run in an environment where $HOME
is not set, it crashes while trying to expand_path "~". The patch
uses Ruby's ENV['HOME'] instead of "~", which sanitises the
expansion.
(FACT-335) implement GCE virtual fact
(FACT-353) Set LC_ALL environment variable to "C" for child processes.

Adding LC_ALL => C for the with_env call in execute.  This will ensure
that child processes that do not check LANG will output using a C
locale if they respect LC_ALL instead.
(FACT-335) Add GCE metadata facts

Implementation derived from d7c863eb.
Merge pull request #696 from peterhuene/fact/353

(FACT-353) Set LC_ALL environment variable to "C" for child processes.
(FACT-593) Remove dependency on route binary from dhcp_servers fact

Previously, the dhcp_servers fact assumed that the route binary
was present, which it then tried to use to determine the primary
interface. This commit updates that fact to instead use /proc/net/route
to retrieve the same information.
Merge branch 'pr/697' into facter-2

* pr/697:
  (FACT-335) Add GCE metadata facts
  (FACT-335) implement GCE virtual fact
Merge pull request #699 from whopper/dhcp_route_fix

(FACT-593) Remove dependency on route binary from dhcp_servers fact
(maint) Avoid repeated fact evaluation against different loaders

Commit 4d937456e fixed an infinite recursion problem where Facter could load
a fact, e.g. ec2, and outside of the setcode body, the fact could reference
another fact, e.g. macaddress, that had not yet been evaluated. This results
in a fact cache miss, causing Facter to reload all facts, including the
original one, e.g. ec2, leading to an infinite loop.

The spec test was written to load nosuchfact.rb, which contained ruby
code that tried to resolve :nosuchfact, causing a cache miss, and
to ensure we didn't infinitely recurse.

However, the spec test did not account that there are two loaders in play,
so if you run:

    $ bundle exec rspec spec/unit/util/loader_spec.rb
    Already evaluated rest at /Users/josh/work/facter/lib/facter/ec2.rb:4, reevaluating anyways
    Already evaluated rest at /Users/josh/work/facter/lib/facter/ec2.rb:21, reevaluating anyways

The reason is because the spec test creates a loader that defines the
ec2 fact and its rest resolution. However, when nosuchfact.rb is loaded,
it calls Facter.value, which delegates to a different loader than the one the
test created. As a result, the ec2 fact is evaluated twice.

This commit simplifies the spec test to ensure that Kernel.load is only
called once for a given fact.
(FACT-570) Remove windows-pr gem when facter packaged as a gem

Commit 60976022a8 removed the dependency from facter's Gemfile, but
not project_data.yaml.
(maint) Move misplaced confine statement in dhcp_servers fact

Previously, one confine statement was nested within another, meaning
that every time we invoked the suitable method, we changed the number of
confines.
Merge pull request #700 from whopper/dhcp_confine_fix

(maint) Move misplaced confine statement in dhcp_servers fact
(#190) Don't set external facts when ENV['HOME'] is nil
Merge branch 'pull-691' into facter-2
(FACT-592) Unbreak swapfree/swapsize facts on OpenBSD

On OpenBSD the "swapctl -s" output also reports the blocksize which
must be taken into account. Also the scaler was incorrectly reporting
terabytes of swap instead of gigabytes.
Merge branch 'pull-698' into facter-2
(FACT-664) Fix swap facts for SmartOS container

Inside a SmartOS container swap facts report 0 for size and free even
though a swap volume is allocated. This removes the leading '/' to match
the smartos swap format.
Merge branch 'pull-664' into facter-2
(FACT-476) Make the 'processor' fact for OpenBSD consistent with other operating systems.
Merge branch 'pull-671' into facter-2