Take into account source directory from original configuration for the generated repository links (#152)

* Allow the test environment to keep the originally sat 'source' value.

* Add a test case and a fix for the ignored source setting in the configuration file.

* Prepend the TEST_DIR only when the source configuration is not set to an absolute path (making it absolute in the process)

* Fix the definition of the relative repository paths, and fix the test feature to properly use the configured source directory.

See #147

See #147

See #129

See #129

This permits easier iteration over an arbitrary number of authors.

See #127

See #124

 * Add group_by option, to group bibliography entries.
 * Add proper names for entry types, and months.
 * Add support for multilevel sorting.

Removed tag option for raw bibtex entry.
Added a note in the documentation on the usage of this option.

See #117

See #118

fixes #112

see #108

see #84

This simple 'solution' returns all entries for ``--max 0``.  Now, to
avoid this the logic of ``offset`` and ``max`` needs to become more
complex - unless I am missing an obvious solution.

see #82

this time add add tests to prove it