add matchers for chefspec

Create matcher for chefspec to test LWRP.

```ruby
it 'create users' do
  expect(chef_run).to add_htpasswd('user1')
  expect(chef_run).to add_htpasswd('user2')
  expect(chef_run).to add_htpasswd('user3')
end 
```
```ruby 
it 'delete users' do
  expect(chef_run).to add_htpasswd('user1')
  expect(chef_run).to add_htpasswd('user2')
  expect(chef_run).to add_htpasswd('user3')
end 
```
```ruby
it 'overwrite user' do
  expect(chef_run).to overwrite_htpasswd('user1')
end 
```