Checking options before applying syntax highlighting for HTML output
Merge pull request #907 from KholdStare/fix-no-highlight

Checking options before applying syntax highlighting for HTML output
Updated a test whose output changed due to last commit.
Docx writer:  Make `--no-highlight` work properly.
Default epub CSS: Removed highlighting styles.

These are added automatically to individual chapter files,
depending on the highlighting style selected on the command line.
Simplified margin fields in default epub CSS file.
Makefile:  --enable-benchmarks no longer works with cabal install.
Tweaked travis script to use cabal-dev.
Another attempt at the travis build spec.
Another attempt at .travis.yml.