code: function getImports(moduleTree) {
  	var imports = [];
  
  	function addImport(name) {
  		if ([].indexOf.call(imports, name) == -1) {
  			imports.push(name);
  		}
  	}
  
  	traverse(moduleTree, function(node) {
  		// import {} from 'foo';
  		// export * from 'foo';
  		// export { ... } from 'foo';
  		if (node.type == "EXPORT_DECLARATION") {
  			if (node.declaration.moduleSpecifier) {
  				addImport(node.declaration.moduleSpecifier.token.processedValue);
  			}
  		}
  		else if (node.type == "IMPORT_DECLARATION") {
  			addImport(node.moduleSpecifier.token.processedValue);
  		}
  	});
  
  	return imports;
  }
docs: given a syntax tree, return the import list