Fix link code.

Add code so jumps from link_target work.
Add code so jumps from link_reference to sections work.
Added code to edit xxx_ references that point to xxx.html
by converting xxx.html links to xxx.rst before editing.
Merge pull request #76 from ldhughes/link_fixes

Fix link code.
Update rhythm.css
Merge branch 'master' of github.com:Rykka/riv.vim
Fix create#link without always return phase
add Todo
Fix create#link