Ebookmaker

- remove encoding meta element originating in HTML5 source from EPUB2 files, as it was causing validation failures.
- fix bug when an XHTML source file set an xml:lang attribute

- use tidy for _all_ html source files
- addressed long-standing issue where images referenced in css were not included in epubs. This issue surfaced because the images were also missing from generated files.
- addressed some simple issues preventing derived HTML5 files from validating. More complex issues involving incompatibilities between XHTML and HTML5 have been enumerated and will be addressed in subsequent updates.
- removed http-equiv meta elements for Content-Type and Content-Style-Type
- set lang attribute when xml:lang attribute is present
- removed duplicate encoding meta elements introduced by HTML5 source.
- removed type attribute from style elements
- update requirements so that stand-alone installs will work better

- more aggressive session closing

- fix crash when source document contains html comments

- Using libgutenberg 0.8.7, which includes the type of meta tags used in HTML5.
- Ebookmaker was not saving the derived HTML files if the main source file was in the output directory. This prevented online Ebookmaker to from displaying the files. Now, Ebookmaker will put derived files in an "out" directory. This turned out to require some code restructuring.
- The pseudo-xhtml files produced by 0.11.5 were cause problems with browser compatibility, most noticeably by doubling break elements. It turns out that the quirky output from lxml was caused by xml namespacing of elements. when xml namespaces were removed, the html output method worked as desired, resulting in files that in many cases validated as html5. This solved a number of problems for us, and puts us in a position to start remediating problem files in the backfile in preparation for EPUB3.
- The encoding for all python source files was changed to UTF8. A mis-encoded python file caused a problem with mdashes in titles.
- Sessions are now closed after every set of jobs. Ebookconverter was running out of Databse connections.
- Some superfluous logging was removed.
- There is documentation for the changes introduced in version 0.11

- fix bug in stand-alone kindle generation