The "PeriodInSuiteName" Rule does not run on directory names

[bkhouri]

A test suite can be a folder, and running the "PeriodInSuiteName" does not get triggered on the a folder.

Reproducible: 100%

Steps to Reproduce:

1. Create the following directory structure

   ├── RFLintTest
   │   ├── MyLinter.Testing.robot
   │   └── SubSuite.WithPeriod
   │       ├── Test.robot
   │       └── __init__.robot
   

2. Run rflint --ignore all --error PeriodInSuiteName --recursive ./RFLintTest

   $ rflint --ignore all --error PeriodInSuiteName --recursive ./RFLintTest/
   + ./tests/RFLintTest/MyLinter.Testing.robot
   E: 0, 0: '.' in suite name 'MyLinter.Testing' (PeriodInSuiteName)