Source selected vimscript

You can just call :exec to run the contents of a buffer (because it's
an expression). Works for multiple lines.

Via sjl:
https://bitbucket.org/sjl/dotfiles/src/e6f6389e598f33a32e75069d7b3cfafb597a4d82/vim/vimrc#cl-406
sub: Add hiinterestingword

Easy map to highlight words or selection.
sub: Add rsi and undo some of its mappings

There's something to love in rsi, but I use some of these keys already,
so unmap them. Move my Esc map to zpersonalized so it doesn't get lots
among other junk.
sub: Extract Gogo command into vim-gogo

Seems pretty useful, so I've extracted it to make it easier to share.