Add docs to help users upgrade from < 1.0, fixes #877

* Help with new command line usage
* Help with deprecated flags
* Help with baseurl
* Help with drafts
Hard line wrap FTW!
s/problematically/programmatically/, props @mojombo
De-deprecate `--safe`, props @mojombo
Note that `--auto` is not `--watch`
clean up language a bit to clarify meaning
Add draft functionality explanation to upgrading docs
First pass at baseurl documentation
s/root/source/, props @parkr
fix typo in draft post explanation, props @parkr
Direct users to the proper command when previewing drafts.
clarify baseurl usage
quick shout out to jekyll new
Make --config usage more explicit.

See https://github.com/mojombo/jekyll/pull/965#discussion_r3797116 and https://github.com/mojombo/jekyll/pull/965#discussion_r3797085

Props @parkr.
Clarify new way to do server and auto, props @parkr

see https://github.com/mojombo/jekyll/pull/965#issuecomment-16396829
plurlize file(s)
hard wrap *all* the things!
remove stray comma
s/--server/serve
moar hard word wrapping