Added whereExist and whereNotExist

[ejhayes]

This includes template helpers whereExist and whereNotExist. I found myself looking for containers that did not have an environment variable and wanted an easy way to query containers (existing where function didn't seem to work with "" or nil).

[thaJeztah]

I think there's an error in the Dockerfile, because it now refers to your repository, not the "main" repository.

(Perhaps the Dockerfile changes should not be part of the pull-request)

[ejhayes]

Alright removed - thanks for pointing that out @thaJeztah

[thaJeztah]

Hehe, no sweat, easy mistake to make, I just spotted it :)

[jwilder]

Thanks!

[ejhayes]

Thanks @jwilder - want to add this to 0.3.7 or 0.3.8?

[md5]

@ejhayes I just thought I'd point out that Git tags should generally not be changed after they're created, so the thing to do would be to cut a new version.

[ejhayes]

@md5 totally makes sense. This should be in 0.3.8 in then :)

[md5]

🤘

[jwilder]

Yeah... will go in 0.3.8.