Merge branch 'i18n-momentjs' of https://github.com/thierrytiti/converse.js into thierrytiti-i18n-momentjs

Conflicts:
	converse.js

Also refactored the code to adhere to the style guide.

This is to deal with reconnects. Originally @thierrytiti checked for
`connection.connected` but I think that might still pose a problem when
reconnecting is in process and the user is not yet authenticated again.

This makes pull request #426 unnecessary.

- Add new config option csi_waiting_time for CSI support.
- The auto_away and auto_xa options won't send out CSI stanzas if csi_waiting_time is 0
- Update docs and add tests for both features.

I recently added keepalive functionality to Strophe, similar to what was
already in converse.js. It's stable enough now that we can rely on it
instead.

This is because "pagehide" is fired in more situations and because unload
is not supported on mobile Safari.

We "use strict" outside of the function that gives issues on Safari.

At some point an improbable condition reached a typographic error.

Also update the contributor guidelines to mention the styleguide.

Hide server label in room panel when input is hidden

Small german locale improvements

* Rename onConnStatusChanged to onConnectStatusChanged
* Provide human readable debug feedback on onConnectStatusChanged

Split the code into two new methods for the prebind and non-prebind
usecase.

More small improvements to german locale

Also fixed a CSS bug. Chat box's width wasn't responsive.

mentioning plugins architecture refactoring.

Improve de locale

- TrimChats was called before a newly maximized chat had its final width which
  prevented it from working as intended.
- We cannot check for available space by using the width of the #conversejs
  element anymore, since it now has variable (auto) width. So we check against
  the body width instead.