remove unnecessary uses of `new` with native constructors

ref https://github.com/jashkenas/underscore/pull/1616#issuecomment-43547113
fixes #1641: _.min iterator should accept context
update npm during travis CI run to fix transitive caret (^) dependencies
fixes #1608: integrate eslint into testing process
Merge pull request #1616 from michaelficarra/GH-1608

fixes #1608: integrate eslint into testing process
remove unneeded predicate check
Merge pull request #1643 from mehdishojaei/remove-unneeded-predicate-check

remove unneeded predicate check
Abstract _.pick and _.omit via pick wrapper