update for PR https://github.com/metapolator/metapolator/pull/197 to current master.

A test case is:

    $ mp import /tmp/Merriweather-Regular-Subset.ufo mw1  >| /tmp/out.txt 2>&1
    $ mp export mw1 /tmp/output1.ufo
    
    $ xmllint --format /tmp/Merriweather-Regular-Subset.ufo/fontinfo.plist >| /tmp/orig
    $ xmllint --format /tmp/out2.ufo/fontinfo.plist >| /tmp/new
    $ diff -Nuar /tmp/orig /tmp/new
    --- /tmp/orig   2014-10-09 11:53:02.107295855 +1000
    +++ /tmp/new    2014-10-09 11:52:38.020519437 +1000
    @@ -1,5 +1,5 @@
     <?xml version="1.0" encoding="UTF-8"?>
    -<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-    1.0.dtd">
    +<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
     <plist version="1.0">
       <dict>
         <key>familyName</key>