New image requests validator

Added Image Facter
New CSS requests validator

Added CSS Facter
New JavaScript requests validator

Added JS Facter
Added Validator: Image without alt attribute (Closes: #6)
Added Validator: Anchors without any text (Closes: #5)
New Meta Tags validator

Added Meta Tags Facters
Added Validator: Page without meta tags
Added Validator: Meta Robots with value of {noindex, nofollow}

Closes: #7
Added Validator: Required meta tags (Closes: #4)
Fixed toredis dependency