Css Changes for Gallery categories section

-- removed ".thumb-item-head-wrapper" and "thumb-item-head" classes as
they seem pretty redundant, move margin information from
".thumb-item-head" to ".thumb-item"
-- it doesn't sound intuitive to have caption/title related styles under
".thumb-item-image-icon" class, please move those styles to
".thumb-item-title" and remove ".thumb-item-image-icon"
-- removed ".image-loaded" class from ".js-image"
-- removed margin from h4 under ".thumb-item-title"