Update Quarterly's README:

• Make timeline clearer.

• Remove section 2): its content is now clearly included in section 0) just after the timeline.

• Merge section 1) and section 3) and sort their elements more consistently.

• Remove inexistent e-mail address for EuroBSDcon and explain that reports about it should be asked to people that went to it and not to the organization itself.

Submitted by: salvadore@
Differential Revision: https://reviews.freebsd.org/D22558