Vim: add VISUAL placeholders to JavaScript snippets

This allows me to use the snippets to wrap code selected from visual
mode.
Vim: Add switch and case JavaScript snippets
Vim: add indentatino -> indentation abbreviation

I've found myself typing this incorrectly a lot lately. This should put
a stop to that quickly.
Vim: enable jsxcs as a syntastic checker for JavaScript files

JSXCS is a wrapper around JSCS that allows it to work on JSX files.