Added testing in JRuby for Travis.
[vcloud_director] Mocking for tasks.
[vcloud_director] strftime not iso8601 for ruby 1.8.7
[vcloud_director] Consistent usage of ensure_list! in get_disk.
[vcloud_director] Fix ruby 1.9-isms in media_tests.
Removed errant :host argument
Add a reload() method to the vSphere service.

Like other compute services, it would be useful if vSphere also
supported reload(). The method should reestablish any session state
required for Fog when network errors arise (EPIPE, etc).

Fixes: #2307
Merge pull request #2311 from maginatics/vsphere_reload

Add a reload() method to the vSphere service.
Merge pull request #2309 from jtopper/master

Removed errant :host argument
Semantic Versioning (and Pessimistic Versioning Constraint) notice

I noticed some projects using Fog are setting very specific versioning constraint.  For example, https://github.com/mitchellh/vagrant-rackspace/issues/34 happened because both vagrant-aws and vagrant-rackspace are using 3 digits of precision.

The fog RELEASE.md says that Fog follows semantic versioning.  Several other projects have put up notices suggesting to use 2 digits of precision for projects that follow semver.  See https://github.com/intridea/multi_json, for example.

I added a similar notice, but softened the language because I don't think there is a clear understanding on what semantic versioning means for a project like Fog, which has multiple providers backed by services that are all evolving at their own pace.
Merge pull request #2302 from nosborn/vcloud_director_task_mocking

[vcloud_director] Mocking for tasks.
Don't load a couple MRI-only development dependencies on JRuby.
Temporary hack around #2279 to get fog loading on JRuby.

The plan is to get things largely building in JRuby and then tackling #2279 separately.
Added logging message for JRuby users to know they're at a disadvantage.
Merge pull request #2315 from nirvdrum/jruby_fixes

JRuby fixes.
Merge pull request #2312 from nirvdrum/add_jruby_to_travis

Added testing in JRuby for Travis.
[core] Make `ruby-libvirt` dependency optional

The `ruby-libvirt` dependency was commented out since it is rarely used
and a pain for developers to prepare.

The comment was removed in https://github.com/fog/fog/commit/b373e55a8f32b24c11fe4b20e773c1428df9d811
to protect JRuby but made it a requirement for MRI (& others).

This adds another guard based around the setting of `FOG_USE_LIBVIRT`
environment variable.

This hopefully will mean anyone wanting to use it can just set that
rather than editing the gemspec.

Fixes #2316
[jruby] Ignore failures until fully supported

JRuby is now being tested but does not pass yet so I'm ignoring the
failures in Travis until support is finalised.
Merge pull request #2317 from fog/remove_libvirt_dependency

[core] Make `ruby-libvirt` dependency optional
Scope the Unicode module so NameErrors make more sense.