Allow ImportDeclaration kind to be undefined.

For example, given `import "foo";` the `kind` property of that node will be `undefined`.
Merge pull request #54 from eventualbuddha/import-declaration-kind-can-be-undefined

Allow ImportDeclaration kind to be undefined.
Bump NPM version to 0.4.10 in preparation for publishing.
Use depd for deprecation warnings.

Closes #60.
Bump NPM version to 0.4.11 in preparation for publishing.
Update ES6 module AST types for @caridy.

Closes #62.
merging @benjamn custom branch
final touch for modules