Does it make sense to keep a README.rst and a README.md??

Copy latest changes from README.md

The spec allows for `image/svg+xml` to be included without a fallback,
but does not mention `image/svg`. This causes violations in epubcheck
when mkepub inserts an SVG file.

https://www.w3.org/publishing/epub3/epub-spec.html#tbl-core-media-types

It doesn't make sense to measure the test coverage of the tests
themselves, so exclude them from coverage.py.

This corrects some spurious Coveralls complaints in GitHub PRs.

Also remove some stray whitespace at the end of the license_file line.

The EPUB spec allows for Dublin Core metadata terms. This commit adds
support for them to the package.opf template.

No API change is necessary—all metadata is already passed through to the
template.

It is the client's responsibility to ensure that only valid DC
terms are supplied (just as page content HTML).

https://www.w3.org/publishing/epub3/epub-packages.html#sec-metadata-reserved-prefixes
https://www.dublincore.org/specifications/dublin-core/dcmi-terms/

Use `image/svg+xml` media-type for SVG files.

Exclude mkepub/tests/* from coverage.py

Add dcterms to package.opf template

Add test.log to .gitignore