Update tutorial, see issue #13578
mark non-immediate by-value parameters as non-null
handle attributes for non-immediate types first

Slices are non-immediate and were not having these attributes applied.
auto merge of #14439 : thestinger/rust/nonnull, r=luqmana
auto merge of #14374 : swgillespie/rust/swgillespie-tutorial, r=alexcrichton

The current tutorial says that the only way to get master is to build from source, which isn't true anymore - nightly binaries and an installer for Mac OS X are now available at the install page: http://www.rust-lang.org/install.html . Feedback very much welcome! Addresses issue #13578.
Improve docs for core::tuple
auto merge of #14440 : Sawyer47/rust/tuple-doc, r=alexcrichton
fix MIPS target