Improved INSTALL instructions.
Added Text.Pandoc.Process (pipeProcess).

A souped up version of readProcessWithErrorCode that uses lazy bytestrings
and allows setting environment.
Use pipeProcess in Text.Pandoc.PDF.
Pass writename as argument to filters.

This way filters can figure out what the target format is
and react appropriately.

Example:

    #!/usr/bin/env runghc
    import Text.Pandoc.JSON
    import Data.Char

    main = toJSONFilter cap
      where cap (Just "html") (Str xs) = Str $ map toUpper xs
            cap _ x = x

This capitalizes text only for html output.
Preliminary support for new Div and Span elements in writers.

Currently these are "transparent" containers, except in HTML,
where they produce div and span elements with attributes.
Adjustments for new Format newtype.
Updated tests for new Format.
Use query instead of queryWith.
Use walk, walkM in place of bottomUp, bottomUpM when possible.

They are significantly faster.
Added Tests.Walk.

This verifies that walk and query match the generic traversals.
Initial implementation of tables in dokuwiki writer (#386)

Todo: alignment, and headings
Options: Changed `writerSourceDir` to `writerSourceURL` (now a Maybe).

Previously we used to store the directory of the first input file,
even if it was local, and used this as a base directory for
finding images in ODT, EPUB, Docx, and PDF.

This has been confusing to many users.  It seems better to look for
images relative to the current working directory, even if the first
file argument is in another directory.

writerSourceURL is set to 'Just url' when the first command-line
argument is an absolute URL.  (So, relative links will be resolved
in relation to the first page.)  Otherwise, 'Nothing'.

The ODT, EPUB, Docx, and PDF writers have been modified accordingly.

Note that this change may break some existing workflows.  If you
have been assuming that relative links will be interpreted relative
to the directory of the first file argument, you'll need to
make that the current directory before running pandoc.

Closes #942.
PDF:  Add suggestion to use --latex-engine=xelatex on encoding error.
ODT/OpenDocument writer:  Minor changes for ODF 1.2 conformance.

See #939.  We leave the nonconforming contextual-spacing attribute,
which is provided by LibreOffice itself and seems to be supported.
reference.odt:  Change generator in meta.xml to Pandoc.
Text.Pandoc.Compat.Monoid: Small improvements to the (<>) definition.
Removed `--print-sample-lua-writer`, added `--print-default-data-file`.

Closes #943.
Added module for writing python scripts, with several examples.

See scripts subdirectory.
Commented python modules/sample scripts.
Added graphviz.py example script.