Tabindex values should equal 0

[nickmarden]

We were alerted by a customer that our rails serp is failing their accessibility scanner, because we have tabindex greater than 0. Upon investigation, we've learned that tabindex=0 is best practice, any other values are discouraged, and also that our rails serp doesn't have tabindex=0 anywhere.

All verticals of rails SERPs should be checked and tabindex values updated to 0.

search_consumer SERPs can be ignored; see #34.

[nickmarden]

Anyone looking to take this on should communicate with the Search.gov team about which accessibility testers (e.g. WAVE, AXE, or others) should be considered authoritative for determining compliance of the current or modified SERPs.

[dawnpm]

False positive determined Nov 2018. See SRCH-163.