content/bootcamps: Rename boot camps to bootcamps/YYYY-MM-DD-SLUG.html

$ for x in content/bootcamps/201*; do
> DATE=$(sed -n 's|.*startdate" content="\(.*\)" />|\1|p' "$x");
> git mv $x $(echo $x | sed "s|bootcamps/[0-9]\{4\}-[0-9]\{2\}|bootcamps/$DATE|");
> done
content/blog: Remove startdate metadata

Now that it's encoded in the filename, there's no need for a separate
metadata field.

$ for x in content/bootcamps/20*; do sed -i '/meta name="startdate/d' $x; done