Step version numbers to 3.20
Removed old version 2.14 of ePub
Issue #15

When processing the HTML for external references, the NameSpaces set in
the html element was discarded, leading to DOM errors.
Issue #16

* Fixed: An issue, where PNG images exceeding the maximum specified
sizes were broken during resizing.
* Fixed: Issue #16, where ePub 3 multimedia needed to be added to the
automatic chapter processing.
* Fixed: Potential issue related to Issue #16 with loading large files
from external sources, where these might result in memory errors. These
will now be loaded into a temp file on the server, before being added to
the book.
resolveMedia/Image fix

Functions now try to find the files with and without the docRoot.
function not referenced with $this
Updated revision text
Resolve Merge issues
Merge pull request #19 from Grandt/3.20

* Fixed: Issue #15, where name space declarations were erroneously stripped off the html tag of added chapters.
* Fixed: An issue, where PNG images exceeding the maximum specified sizes were broken during resizing.
* Fixed: Issue #16, where ePub 3 multimedia needed to be added to the automatic chapter processing.
* Fixed: Potential issue related to Issue #16 with loading large files from external sources, where these might result in memory errors. These will now be loaded into a temp file on the server, before being added to the book.
* Fixed: Issue #17, where a function was called as a global.