Allow configuration of etcd request timeout

[tanguy-ortolo]

Hello,

Using remco with a rather large etcd database, we noticed that, immediately after an update, the time for a read request to complete and start returning data can exceed the defined timeout of three seconds.

For now, we are using our own, modified remco with a different hardcoded timeout, but it would be better to be able to configure it. This is the point of PR #99. Please note that the easyKV report and PR need to be addressed first.