Migration - added description to topics

[#5]
Added description in views

[#5]
Added model topic validation and decorator

[#5]
Added item_description css class

[#5]
Fixed item_description css class alignment

[#70]
Converted css syntax to sass in item_description

[#70]
badge should be centered verticaly
Updated readme file
Merge pull request #70 from netguru/add_description_to_topics

Add description to topics