$APP_NAME and $APP_DEPLOY are required when emitting metrics, inject them.
Get Web using new setup.
Log.count takes specified value and extra data.
Explicit Log.measure.
Use measure in time.
Get to ms.
add source to all log lines and fix tests
Merge pull request #17 from heroku/standardized-metrics

Changes to Vault::Log metrics support

Changes Vault::Log methods to make it easy to emit metrics following our best practices.

An upgrade note: both $APP_NAME and $APP_DEPLOY are now required when using the Vault::Log metrics helper methods.

PR with necessary changes to vault-usage to make use of these changes at heroku/vault-usage#121.