Fix Option::unwrap_err.
Switch chain calls to use Option::chain method
std: modernize net_url

This switches over to using structs and send_maps for
query string parsing.
bump 0.5 => 0.6, redirect some URLs in docs.
update after/syntax/rust.vim for removal of <-
Implement BigInt and BigUint.
Move BigUint and BigDIgit to std::bigint.
Convert std::bigint to explicit self.
Impl Zero, One of BigInt, BigUint
Convert @[BigDigit] to ~[BigDigit]
tests: Add test case. Closes #3250
Emit a type error for integer literals where the expected type is char

For example, in let x: char = 42; This was an ICE and is now a
proper type error, as per #3477
Remove xfail-fast from trait-composition-trivial
update mandelbrot to pipes, a few other updates
Fix example.
Merge pull request #4271 from ejholmes/ffi-crypto

Fix example in FFI tutorial.
Fix example.
Add Eric Holmes to AUTHORS
Add Martin DeMello to AUTHORS
Merge pull request #4272 from ejholmes/crates-minimal-example

Fix example in 13.3.