Remove docs and point to ones on dartlang.org.

app/doc/pub-upgrade.markdown

----
-title: "Command: Upgrade"
----
-
-    $ pub upgrade [PACKAGE]
-
-Without any additional arguments, `pub upgrade` gets the latest versions of
-all the dependencies listed in the [`pubspec.yaml`](pubspec.html) file in the
-current working directory, as well as their [transitive
-dependencies](glossary.html#transitive-dependencies), to the `packages`
-directory located next to the pubspec. For example:
-
-    $ pub upgrade
-    Dependencies upgraded!
-
-When `pub upgrade` upgrades dependency versions, it writes a
-[lockfile](glossary.html#lockfile) to ensure that future [`pub
-get`s](pub-get.html) will use the same versions of those dependencies.
-Application packages should check in the lockfile to source control; this
-ensures the application will use the exact same versions of all dependencies for
-all developers and when deployed to production. Library packages should not
-check in the lockfile, though, since they're expected to work with a range of
-dependency versions.
-
-If a lockfile already exists, `pub upgrade` will ignore it and generate a new
-one from scratch using the latest versions of all dependencies. This is the
-primary difference between `pub upgrade` and `pub get`, which always tries to
-get the dependency versions specified in the existing lockfile.
-
-## Upgrading specific dependencies
-
-It's possible to tell `pub upgrade` to upgrade specific dependencies to the
-latest version while leaving the rest of the dependencies alone as much as
-possible. For example:
-
-    $ pub upgrade unittest args
-    Dependencies upgraded!
-
-Upgrading a dependency upgrades its transitive dependencies to their latest
-versions as well. Usually, no other dependencies are updated; they stay at the
-versions that are locked in the lockfile. However, if the requested upgrades
-cause incompatibilities with these locked versions, they will be selectively
-unlocked until a compatible set of versions is found.
-
-## Getting a new dependency
-
-If a dependency is added to the pubspec before `pub upgrade` is run, it will
-get the new dependency and any of its transitive dependencies and place them in
-the `packages` directory. This is the same behavior as `pub get`.
-
-## Removing a dependency
-
-If a dependency is removed from the pubspec before `pub upgrade` is run, it
-will remove the dependency from the `packages` directory, thus making it
-unavailable for importing. Any transitive dependencies of the removed dependency
-will also be removed, as long as no remaining immediate dependencies also depend
-on them. This is the same behavior as `pub get`.
-
-## Upgrading while offline
-
-If you don't have network access, you can still run `pub upgrade`. Since pub
-downloads packages to a central cache shared by all packages on your system, it
-can often find previously-downloaded packages there without needing to hit the
-network.
-
-However, by default, pub will always try to go online when you upgrade if you
-have any hosted dependencies so that it can see if newer versions of them are
-available. If you don't want it to do that, pass the `--offline` flag when
-running pub. In this mode, it will only look in your local package cache and
-try to find a set of versions that work with your package from what's already
-available.
-
-Keep in mind that pub *will* generate a lockfile after it does this. If the
-only version of some dependency in your cache happens to be old, this will lock
-your app to that version. The next time you are online, you will likely want to
-run `pub upgrade` again to upgrade to a later version.