remove docs on installing pygments

This is no longer needed as stated by @parkr in #1021,
as jekyll now comes bundled with pygments.rb.

Fixes #1021.
Update gemspec for new page-based docs.
Merge pull request #1079 from maul-esel/docs-remove-pygments

Remove docs on installing pygments
Update history to reflect merge of #1079
Turn off relative permalinks on Jekyll docs.
Merge branch 'master' into changelist_page
Moved changelist to /history directory.
Updated rakefile to support new directory and parsing structure.