highlight ^old^new pattern

by extending the already in place mechanism of checking for the first
histchar to check for the second as well
Merge pull request #135 from arcan1s/patch-1

Update README.md
Resolves slow performance in brackets highlighter
Chaned main highlighter alorithm to resolve issue #77
Add 'line' highlighter for the whole buffer
zle: don't override yank/yank-pop

`yank-pop` relies on the fact that the last zle command is `yank` or
`yank-pop` to work correctly. Rewriting them prevents this check to work
correctly breaking `yank-pop`.

This fix just disallow overriding of those two zle commands. As a
side-effect, syntax highlighting will not happen when using.

This fixes #99.
Merge pull request #143 from vincentbernat/fix/yank-pop

zle: don't override yank/yank-pop
Merge pull request #142 from jcassee/master

Add 'line' highlighter for the whole buffer
Merge pull request #134 from sonnym/enable_quick_history_substitution_highlighting

highlight ^old^new pattern
Merge pull request #140 from randomize/pr_fix_issue_#77

Pr fix issue #77
README: make installation step 1 more accurate

You cannot download just the "script". You need the entire directory/repo.