failiure/failure

Fix misspelling of failure in the fish shell design doc
New -n option for read builtin

Usage: read -n nchars
Reads maximum of nchars characters. If nchars <= 0, there's no limit.
Fix the fix for `commandline -i` in binds
Merge branch 'master' into documentation-update

Conflicts (fixed):
	doc_src/design.hdr