Version call doesn't handle non-numeric version

[beaulac]

On the google cloud app engine, the memcached service responds to a VERSION call with: VERSION App Engine.

This makes this client crash 😢

This is the regex in the version method: /(\d+)(?:\.)(\d+)(?:\.)(\d+)$/ Clearly, it doesn't support anything other than a semver format.

It's nice to have the ability to separate out the major/minor/bugfix of official releases, but throwing an Error when a non-standard version "App Engine" is thrown at it seems excessive.