Change Makefile so it's easier

Now you just type `make book` or `make serve`, without having to add
GITBOOK=`pwd`/node_modules/.bin/gitbook.

Also, now npm installs it automatically on first run.
Why did we cd into stage in the first place

This works perfectly, as far as I can tell.
Merge pull request #328 from GBGamer/makefile

Change Makefile so it's easier
Pipes example: update comments

The comments referred to some obsolete method names.

Also, fixed a spelling mistake.
Merge pull request #329 from mmorearty/patch-1

Pipes example: update comments
Remove proc() and tuple methods

This now builds with HEAD Rust
Merge pull request #330 from steveklabnik/fix_build

Remove proc()
Fix syntax highlighting disappearing on page refresh. Close #194.
Merge pull request #331 from dbbrian/master

Fix syntax highlighting disappearing on page refresh. Close #194.
Fix broken build

Thanks
https://github.com/rust-lang/rust/commit/0669a432a2e09ad08886cb2138dbe9f5d681fb7f
Merge pull request #332 from steveklabnik/fix

Fix broken build
fix: cannot borrow immutable local variable `collected_iterator` as mutable
Merge pull request #338 from rofrol/master

fix: cannot borrow immutable local variable `collected_iterator` as muta...