added support for transformers namespacing

[thau0x01]

Now, users can create namespaced transformers by specifying the subfolder using '/'.

e.g: adonis make:transformer Users/User

// the output file would be
app/Transformers/Users/UserTransformer.js

[rhwilr]

@NeroOficial Thank you for your contribution. 👍
I made some changes, so the code fits the style of the rest of the project. You can expect a new version in the next few days.

[thau0x01]

Thank you man!

[rhwilr]

🎉 Now available in 1.5.1

[thau0x01]

nice man!