Add per-serie options. Fixes #124, References #114, Partly addresses #109
Include DateY fixes from #109
Prevent persistent temp file creation
Adds tests for plot_boject.add_xml_filters

Adds two tests for the add_xml_filters method of a plot object, a round
trip of a non-tree-modifying filter, and a simple tree modifcation that
adds a sub-plot of change bars to a bar plot.
Cleanup a bit and prevent crash with log
Improving coverture and robustness
Merge pull request #126 from sirlark/xml_filters

Adds tests for plot_boject.add_xml_filters
Improve coverage again
Fix show_major_dots + coverage
Coverage again
Add some coverage
Added new option to config 'half_pie' to allow only creating half of a pie chart, for Kozea#123 [Fixes: #123]
Tests for pie
Start working on a render_table method to generate a HTML table with the chart values.
WIP on tables
Remove color limit for legends too. Fixes #128
Make lxml an optionnal dependency
Fix table import
Wrap etree
Parametrize test to test with and without lxml