Provide a way to check version in code #330
Description
metrics is a developing package and new features or critical bugfixes happen often, as well as new releases. There are no explicit way to check what metrics version is used in code when you are providing an optional integration with your module. For example, the only way to check that I'm using metrics 0.9.0 or greater with age buckets and fixed summary under high load is to check require('metrics.collectors.summary').rotate_age_buckets ~= nil, but this check is based on internal structure of the module that could change at any time. It would be nice to have something like require('cartridge.VERSION').