Remove Xpdf from README, until we fix #12.

README.md

@@ -21,17 +21,16 @@ You may need to reload your behaviors or restart Light Table to get
 everything loaded properly.
 
 You'll need TeX installed, of course.  For the PDF viewer, you also need
-the command-line programs `pdftoppm` and `pdfinfo`, part of [Poppler][3]
-or [Xpdf][4].  Linux users should find these in their repositories, if
+the command-line programs `pdftoppm` and `pdfinfo`, part of
+[Poppler][3].  Linux users should find these in their repositories, if
 they aren't already installed.  (On Debian-based systems, they're in the
-*poppler-utils* package.)  A version for Windows is available on the
-[Xpdf download page][5].  The Mac package linked to on that page does
-not contain the pdftoppm binary, but I've heard that `brew install
-poppler` works.
+*poppler-utils* package.)  On Macs, Poppler can be installed with `brew
+install poppler.  For Windows, I've found [these][4] [two][5] sources,
+but I can't attest that they work.
 
 [3]: http://poppler.freedesktop.org/
-[4]: http://www.foolabs.com/xpdf/home.html
-[5]: http://www.foolabs.com/xpdf/download.html
+[4]: http://blog.alivate.com.au/poppler-windows/
+[5]: http://manifestwebdesign.com/2013/01/09/xpdf-and-poppler-utils-on-windows/
 
 Usage
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