Add and verify rules for individual files.

[abose]

• Identify what needs to be done for each file type based on plugins : https://github.com/Skyscanner/whispers/tree/master/whispers/plugins
• html.py
• javascript.py
• json.py
• config.py
• npmrc.py
• yml.py
• xml.py
• uri.py
• shell.py
• plaintext.py

[Mandeep08punia]

npmrc files support: #25

[Mandeep08punia]

json files support: #28

[Mandeep08punia]

code lines fixed #29