Update 'Run tests' section in README files to avoid comfusion

[ilya-khadykin]

There are some exercises which have auto-generated README file and require 'Run tests' section update

List of all affected exercises:

• difference-of-squares
• gigasecond
• hamming
• leap
• nth-prime
• phone-number
• raindrops
• rna-transcription
• robot-name
• roman-numerals

In correct version of README file exercise specific test Spec file should be mentioned (example)

[kytrinyx]

@m-a-ge I am tweaking Configlet so that we can regenerate all the READMEs with the correct filename. See exercism/configlet#48

Once this is merged and a release is cut, we can update the readme template (https://github.com/exercism/groovy/blob/master/config/exercise_readme.go.tmpl) to directly include the text that is currently in the readme insert (https://github.com/exercism/groovy/blob/master/docs/EXERCISE_README_INSERT.md).

We will be able to generate the command to run the tests in the template:

$ groovy ./{{ .Spec.MixedCaseName }}Spec.groovy

So we can delete the readme insert, and put all of it directly into the template like this.

{{- with .TrackInsert }}
{{ . }}
{{ end }}

[ilya-khadykin]

@kytrinyx, thanks a lot for the explanation. Looks like I've missed it.
I should read more about it

In the meantime, I'll close this issue since it isn't valid

[kytrinyx]

There's detailed information here: https://github.com/exercism/docs/blob/master/language-tracks/exercises/anatomy/readmes.md If anything is confusing, please let me know so I can update it!