Change ahs change range key to `r` instead of `c`

ahs = auto-highlight-symbol
This change was made to free `c` to clear persistent
highlighting of search with `<SPC> s c`
Add evil-search-highlight-persist
Remove uneeded `SPC s s ` to initiate ahs
Helm-swoop is now bound to `<SPC> s` prefix
Create searching section in readme