Consider disabling compression by default

[dpb587]

There are potential security implications of enabling the compression features of OpenVPN. Given this is not enabled by default with stock OpenVPN configurations, it should probably not be enabled here by default either. Since this can affect both client and server configurations, it should be part of a major version change.

OpenVPN also discusses the compression topic on their page about VORACLE.

This was originally mentioned in #20.