an image is wroth a thousand words
Add spm support
Only access properties of objects on Context.lookup
Merge pull request #380 from skybet/section-with-length-property

Section with "length" property
solve merge conflicts in spmjs/add-spm-support

Conflicts:
	package.json
Merge branch 'spmjs-add-spm-support'
Merge pull request #327 from videlalvaro/patch-1

an image is wroth a thousand words
key lookup when not in root context with undefined/null value fails,
fixes #397, fixes #409