Fix help not displaying code correctly

airline_powerline_fonts wasn't wrapped in ><, so it displayed as normal
text and threw off the syntax highlighting.
Fix tagging markup in help

Vim help's help-writing describes how to use '' around options and ||
around help links. Use these where possible to give the correct syntax
highlighting (and help vim-scriptease know the correct type to jump to
for ambiguous symbols).
Merge pull request #250 from pydave/fix-help

Minor improvements to help