Small improvements to contributing for accessibility.

Small improvements to contributing for accessibility.

This makes a small number of changes that can help improve onboarding
and diversity of contributors. Key to point out is that the code of
conduct is now one of the first items, to highlight the community
standards (rather than being at the bottom where it can be
overlooked). The use of the work "hack" often is off putting to
many people, so replaced with "work". Additionally, changed
the introduction to highlight a desire to be inclusive.

A follow up you probably could do, is have a "how to prepare the
development environment" aka "what depenedencies do I need for
my distro to build the project.

Much of this has come from experience working with outreach/diversity
experts, and my own experience on

http://www.port389.org/docs/389ds/contributing.html

Signed-off-by: William Brown <william@blackhats.net.au>