First draft
Update release-policy.md
Update release-policy.md
Update release-policy.md
Added a summary table and added info on how long we support versions
Consolidating the sub headers

Also removed the support agreement part
Typos
typos
sentence structure
more sentence structure + email contact
Improved title
typos
Improved wording and readability.
Added colon
Minor adjustments
Merge pull request #474 from Particular/upgrade-guidance

Release policy/guidance for NServiceBus