docs(guide/component) correct usage recommendations

[zuzusik]

Currently in section When not to use Components it is said:

• for directives that rely on DOM manipulation, adding event listeners etc, because the compile
  and link functions are unavailable

But there is a $postLink hook which is described in the same document as follows:

• $postLink() - Called after this controller's element and its children have been linked. Similar to the post-link
  function this hook can be used to set up DOM event handlers and do direct DOM manipulation.

I assume text from the first quote should be changed to something like

• for directives that need to perform actions in compile and pre-link functions, because they aren't available

Thoughts?

[gkalpak]

Sounds reasonable. The initial guide was written before lifecycle hooks (such as $postLink) were implemented.