Sorting out Alt-text on all SVGs. The site logo needs, and now has, Alt-text, while the other SVGs are all decorative (i.e. meaningless) so have had it removed.
Adding empty alt text to all avatar images. These need empty alt text so that screen readers ignore them. They are 'decorative' (the name is already beneath the avatar)
Added ARIA to the company logos, as per advice here: http://stackoverflow.com/a/25084573/1358187 and also here: http://webaim.org/techniques/alttext/
Added alt text to the logo group on the Partner pages
Added alt text to logo groups on Verticals pages.
Updates to the existing Alt-Tags, based on testing through VoiceOver on iOS
Merge branch 'dev' into alt-tags

Conflicts:
	app/pages/basic/index.html
	app/pages/creative-industries/index.html
	app/pages/gyms/index.html
	app/pages/invoicing/index.html
	app/pages/membership/index.html
	app/pages/partners/clearbooks/index.html
	app/pages/partners/freeagent/index.html
	app/pages/partners/index.html
	app/pages/partners/kashflow/index.html
	app/pages/partners/pitchero/index.html
	app/pages/partners/xero/index.html
	app/pages/professional-services/index.html
	app/pages/property/index.html
	app/pages/saas/index.html
	app/pages/sports-clubs/index.html
	app/pages/stories/bluesky/index.html
	app/pages/stories/crossfit-tonbridge/index.html
	app/pages/stories/greater-anglia/index.html
	app/pages/stories/has-bean-coffee/index.html
	app/pages/stories/rock-choir/index.html
	app/pages/stories/spencer-hockey/index.html
	app/pages/stories/zest-digital/index.html
	app/pages/subscriptions/index.html
remove these again - got added during merge with dev from OLD branch
rename alt text to "GoCardless Dashboard interface"
Merge pull request #310 from gocardless/alt-tags

Alt tags for accessibility