Task to manage chefignore file

[athompson-r7]

The aim of this change is to try to detect the presence of the ignore files/directores in the chefignore file and try to add them if they are missing.

In addition to adding the ignore files to the chefignore file we are displaying a warning to the user suggesting they update their chefignore file in the source repo so we don't have to do this.

Finally, we copy the chefignore file to the .builderator so that the berks binary can find and use it.

The content we are adding looks like this:

.builderator

We are no longer nesting vendored cookbooks, so this fixes #88.

$ find .builderator -name rapid7-logstash-server

$ find .builderator/cookbooks | wc -l
     813

[dgreene-r7]

Looks good! 👍