doc: remove out of date documentation

doc.go

 /*
 IPFS is a global, versioned, peer-to-peer filesystem
-
-There are sub-packages within the ipfs package for various low-level
-utilities, which are in turn assembled into:
-
-core/...:
-  The low-level API that gives consumers all the knobs they need,
-  which we try hard to keep stable.
-shell/...:
-  The high-level API that gives consumers easy access to common
-  operations (e.g. create a file node from a reader without wrapping
-  with metadata). We work really hard to keep this stable.
-
-Then on top of the core/... and shell/... Go APIs, we have:
-
-cmd/...:
-  Command-line executables
-test/...:
-  Integration tests, etc.
-
-To avoid cyclic imports, imports should never pull in higher-level
-APIs into a lower-level package.  For example, you could import all of
-core and shell from cmd/... or test/..., but you couldn't import any
-of shell from core/....
 */
 package ipfs