LaTeX reader:  Make command macros work everywhere, including non-math.

Environment macros still not supported.
Fixed bug in withRaw.

Didn't correctly handle case where nothing is parsed.
EPUB3:  Don't use the switch statement for mathml.

It is not widely implemented yet.
Documented .bibtex extension for BibTeX.

Closes #662.
Cabal file changes.

* Remove executable and library flags.
* Expose `Text.Pandoc.XML` and `Text.Pandoc.Biblio`.
* Depend on pandoc library in executable, so we don't recompile
  everything.
* Move pandoc.hs from src/ to .
Data files changes.

* Added `embed_data_files` flag.  (not yet used)
* Shared no longer exports `findDataFile`.
* `readDataFile` now returns a strict bytestring.
* Shared now exports `readDataFileUTF8` which returns a string like
  the old `readDataFile`.
* Rewrote modules to use new data file functions and to avoid
  using functions from Paths_pandoc directly.
Moved all data files and templates to data/.
Made `embed_data_files` flag work.
Updated windows installer to use `embed_data_files` flag.
Updated osx installer, since we no longer have a `library` flag.
Fixed benchmark file to find documentation files.
Updated INSTALL with new flags.
Updated windows installer so it doesn't copy data files.

These are now embedded in the binary itself.
Workaround for problem with file-embed.

file-embed uses forward slashes as path separators, even
on Windows.  So we just convert backslashes to forward
before doing a lookup.
Revert "Workaround for problem with file-embed."

This reverts commit 84ed0f055f71f32fc2db1dbe962e83cd0bb0b5d8.
Require file-embed >= 0.0.4.7.

This fixes a bug with embedDir on Windows:  previously
forward slashes were used as path separators.
Makefile: added 'relocatable' target.
Fixed bytestring upperbounds (0.11, not 1.0).
Makefile:  Do submodule updates and install cabal-dev in make prep.
Fixed test suite to use Diff 0.2 API.