Rewrote alerts code
Rewrote alerts code

- Allow modal alerts that must be dismissed (or replaced)
  programmatically.

- No more alert queue, since it hasn't been needed

cityofsomerville/citydash,codeforboston/cornerwise,cityofsomerville/citydash,cityofsomerville/cornerwise,cityofsomerville/cornerwise,cityofsomerville/cornerwise,cityofsomerville/cornerwise,cityofsomerville/citydash,codeforboston/cornerwise,cityofsomerville/citydash,codeforboston/cornerwise,codeforboston/cornerwise