zotero: 4.0.28 -> 4.0.29

Built and tested locally.

From the changelog:
```
Firefox 45/46 compatibility
  * [Zotero Standalone] Save PDFs directly from browsers via the Save to
    Zotero button
  * Requires Chrome connector version 4.0.29; updated Safari connector
    coming soon
  * To convert a standalone PDF attachment to a full item, right-click
    the item and choose “Retrieve Metadata for PDF” or “Create Parent
    Item”.
  * [Zotero for Firefox] Don't show Firefox open/save dialog when
    showing style installation prompt
  * Retry additional file sync failures automatically
  * Fixed potential crash when dragging in files on some systems
  * Fixed potential crash when dragging collections to another library
  * Miscellaneous bibliographic output and word processor integration
    fixes
  * Updated citeproc-js to version 1.1.71
  * Fixed spacing of toolbar icons on Windows/Linux in Firefox 43+
  * Use larger text field for Book Title
  * Make highlight color of selected items list rows on Linux more
    distinct when items pane doesn't have focus
  * [Zotero for Firefox] Improved error message on Firefox login manager
    failure
  * Improved error message when trying to use a later database version
```