Allow to test process parameters

Any parameter that can be queried with `ps` can be used for tests. For
example:

```
describe process("memcached") do
  its(:args) { should match /-c 30000\b/ }
end
```
Merge pull request #321 from vincentbernat/feature/process

Allow to test process parameters
Fix for serverspec/specinfra#28
Merge pull request #322 from serverspec/change-get_process-arguments

Fix for serverspec/specinfra#28
Add to_ary to Serverspec::Type::Base

Because it's needed to json format reporter.
Merge pull request #323 from serverspec/add-to_ary-to-type-base-class

Add to_ary to Serverspec::Type::Base
Bump up version
Bump up dependent version of specinfra
Bump up version
Quick hack for #324

As reported by #324, this code doesn't work since v0.14.0.

```ruby
describe 'sshd daemon' do
  it 'has a running service of ssh' do
    expect(service('ssh')).to be_running
  end
end
```

It seems that ``expect`` notation does not call custom matchers.

One-liner ``should`` notation works fine.
Merge pull request #325 from serverspec/expect-does-not-call-custom-matchers

Quick hack for #324
Bump up version
Subject should be serverspec resource type class

In #325, I wrote "Custom matchers should not check the subject class".

But it's not correct.

Custom matchers should check the class of the argument of match block.

I use ``subject`` as the argument name and it is same as the method name
with RSpec.So it's confusing.

I should not use the name ``subject``, but keep them tentatively.
Merge pull request #326 from serverspec/subject-should-be-resource-type-class

Subject should be serverspec resource type class
Define user and group methods explicitly in Serverspec::Type::Process

Because user and group methods are defined already in Serverspec::Helper::Type.
So method_missing is not called if these methods are not defined explicitly.
Add spec.
Merge pull request #330 from serverspec/explicit-methods-in-process-type

Define user and group methods explicitly in Serverspec::Type::Process
Bump up version
Fix spec for specinfra v0.4.1
Move spec/backend/exec/build_command_spec.rb to specinfra