add "(see below)" to a reference to a new concept

This is because I observed someone reading the tutorial who thought they'd
missed something when they got to the mention of variable bindings.

This patch doesn't reflow the paragraphs so that you can see the semantic
change that I made, and a subsequent patch will reflow this paragraph.

Fixes https://github.com/rust-lang/rust/issues/13570.
reflow with emacs fill-paragraph (fill-column 71)
Guide: Hello, cargo
Add a note that this requires `git`.
Fix capitalization of Issue.

@chris-morgan and @huonw pointed out that even though the feature
is a proper noun, we're using it in a more generic sense here.
tha -> than

Thanks @huonw :heart:
all/some

How could I forsake `rustdoc`? :sweat_smile:

Thanks @huonw.
staticly -> statically

What's funny about this one is that spellcheck caught it, but for
some reason didn't give me the right suggestion, so I assumed that it
wasn't in my dictionary. Oh well.

Thanks @P1start! :heart:
Fix IRC linkage.

Death to `here`!

Thanks @chris-morgan :heart:
StackOverflow -> Stack Overflow

Thanks @chris-morgan
Fixing link to subreddit.

Thanks @chris-morgan :heart:
Move note about $ up

Thanks @chris-morgan :heart:
TIL PATHEXT

Thanks @chris-morgan :heart:
Clarify which curly is being referred to

Thanks @chris-morgan
Note that macros != templates

Good call, @chris-morgan and @cmr!
Fix missing word and some grammar

Thanks @chris-morgan and @P1start! :heart:
C macros, not C++ templates.

@cmr rightfully points out that C macros are worse, and share the
same name.
Fix windows run instructions

Thank you, @stormbrew!
Add one more ignore.

Thanks @huonw
auto merge of #15183 : steveklabnik/rust/hello_cargo, r=huonw

Built on top of https://github.com/rust-lang/rust/pull/15181. https://github.com/steveklabnik/rust/commit/e52719291183d7b4f691a1997c69fd75b8101b07 is the only new commit, you may want to review that separately.

I'm not sure if the car analogy is too glib.