feat(events) account events. closes #59

Deletes tokens and codes when a 'delete' event occurs for
an fxa account.
chore(config): add local loop dev credentials
Merge pull request #169 from vladikoff/loopDev

chore(config): add local loop dev credentials
Merge pull request #168 from dannycoates/notifications

account events
chore(dependencies): updating deps
chore(dependencies): update convict
fix(error): AppError uses Error.captureStackTrace

The AppError constructor accepts a `stack` property in the options,
but previously always assigned `this.stack` to it, leading to Errors
with no stack trace. This was confusing our logging infrastructure, which
tries to improve the format of the `stack` property.

Closes #164