Styleguide is ignoring uppercase category names

[VaclovasV]

Category name is uppercase, but filename is created with lowercase.
Styleguide should not ignore naming casing.

[miezis]

I was able to reproduce this like so:

1. Create new category, all letters lowercased (example: new category).
2. Delete that category.
3. Create new category with uppercase letters (example: New Category).

After these steps the situation is as described by @VaclovasV . It turns out that deleting categories did not delete files and when we were creating new category with same name (except letter cases) new file was not created.

I fixed it to delete category files, when deleting categories and also added category name checking to prevent duplicates in this commit: 742873e

Please review and test it out.