syntax::diagnostics: Color the ^~~~ in green for better visibility

Fixes #7164.
More 0.7 release notes
Show defaults in rustdoc usage message
fix text of tutorials
Update AUTHORS.txt
Minor doc updates to reflect #[deriving(Zero)], and small release notes adjustments.

The `extra::fileinput` module landed just after 0.6 was released, and there are many
more derivable traits.
Usable instructions for generating docs from source
rustc: Fix formatting of --help
Fix take glue of owned trait objects

This finishes the incomplete conversion of unique traits as two-word
allocations started in 211d038abc05c77785f72a31840016517cf218c2.

Fixes #5882, #6717, #7153, #7208.
Expand the deriving(ToStr) implementation
Fix compiling empty fmt! strings
Merge pull request #7230 from Blei/green-squiggle

syntax::diagnostics: Color the ^~~~ in green for better visibility
Merge pull request #7270 from thestinger/doc

accumulated doc pull requests from the queue
Merge pull request #7227 from alexcrichton/issue-7218

Fix compiling empty fmt! strings
auto merge of #7214 : Blei/rust/fix-owned-traits, r=pcwalton

This finishes the incomplete conversion of unique traits as two-word
allocations started in 211d038abc05c77785f72a31840016517cf218c2.

Fixes #5882, #6717, #7153, #7208.
auto merge of #7204 : alexcrichton/rust/deriving-to-string, r=pcwalton

Closes #7180 and #7179.

Before, the `deriving(ToStr)` attribute was essentially `fmt!("%?")`. This changes it to recursively invoke `to_str()` on fields instead of relying on `fmt!`-style things. This seems more natural to me and what should actually be expected.