Uniform method signature
Change how to test generated commands
Update README.md
Change how to test cron type

* Remove shared_cron_examples for easy understanding by loosing abstraction
* Run matcher test and command test at same time

I will change tests for other types like this.
Remove stand-alone commands tests for cron

They were integrated to matcher tests.
Merge pull request #177 from serverspec/fix-cron-tests

Change how to test cron type
Change how to test port type

* Remove shared_port_examples for easy understanding by loosing abstraction
* Run matcher test and command test at same time
Merge pull request #178 from serverspec/change-tests-for-port

Change how to test port type
Change how to test command type
Merge pull request #179 from serverspec/change-how-to-test-command-type

Change how to test command type
Change tests for default_gateway type
Merge pull request #180 from serverspec/change-tests-for-default-gateway

Change tests for default_gateway type
Change tests for iptables type
Merge pull request #181 from serverspec/change-tests-for-iptables-type

Change tests for iptables type
Change tests for host type
Merge pull request #182 from serverspec/change-tests-for-host-type

Change tests for host type
Change tests for interface type
Merge pull request #183 from serverspec/change-tests-for-interface-type

Change tests for interface type
Change tests for linux_kernel_parameter type
Merge pull request #184 from serverspec/change-tests-for-linux_kernel_parameter-type

Change tests for linux_kernel_parameter type