can check windows service startup mode now

[Anirudh-Gupta]

Allows one to check windows services start up mode : https://msdn.microsoft.com/en-us/library/aa384896(v=vs.85).aspx
For example:

describe service('AppMgmt') do
  it { should be_installed }
  it { should_not  be_running }
  its('startmode') { should be 'Manual'} 
end

[ksubrama]

Thank you Anirudh! I'll merge this in once travis goes green.