Add analysis/linting options

[donny-dont]

Currently http just turns on strong mode in its analysis options. If there is a standard for other official dartlang projects then those options should also be enabled.

[donny-dont]

@kevmoo @nex3 would be great to figure that out and then enable the options in one last cleanup so we can pass any travis tests required.

[nex3]

I think just having strong mode enabled is fine.

[srawlins]

Agreed. This is the most standard and common analysis option. Many projects like to enable a set of lints, but that's pretty open to each project.