Introduce property instead of attr

In some situation, attr method calls Module#attr, not Serverspec::Helper::Attributes.
Show deprecated warning when using attr and attr_set
Replace attr to property used in serverspec/helper/detect_os.rb
Remove spec/helper/attributes_spec.rb because it's not needed anymore
Merge pull request #293 from serverspec/introduce-property-instead-of-attr

Introduce property instead of attr
Bump up version
Don't set HostName gotten by vagrant ssh-config to c.host

Because HostName is 127.0.0.1 and it differ from hostname, so SSH connection open/close for each test.
It slows down test processes.
Merge pull request #294 from serverspec/fix-for-vagrant

Don't set HostName gotten by vagrant ssh-config to c.host
Bump up version
check_os returns os release (but currently support redhat only)

Ref: #239
Fix spec
Merge pull request #295 from serverspec/get-os-release

check_os returns os release (but currently support redhat only)
Bump up version
Delete os type cache by mistake, so rececover it
Bump up version
Update WINDOWS_SUPPORT.md

Adding notes for execution of tests on windows.
Merge pull request #297 from vinyar/patch-1

Update WINDOWS_SUPPORT.md
Merge branch 'master' into pat_solaris10
Update to head of main serverspec project