updated readme
readme formatting
still more readme formatting!
remove version dependencies we don't need

* The API is nice and stable around R509::Validity
* Update Gemfile to use https
* Remove Ruby 1.8.7 BS since we don't support that any more
retab from 4 spaces to 2 + remove more 1.8 stuff
Merge pull request #9 from reaperhulk/master

doc updates.

Diffs should be better when the only change on a line is the tab depth.