Updated api.md with node collection query

The node collection (/api/collections/nodes) supports queries against
hostnames and hw_info attributes. Added documentation of this including an
example.
* README.md: fix typo
* NEWS.md: fix typos
* README.md: changed "recipes" reference to "tasks
Prevent duplicate files when streaming download

Per RAZOR-73: Open-uri was causing temporary files not to get cleaned up. This is now using open-uri's tempfile without creating a duplicate. Added tests for redirect and cleanup for post-test files.