Document and Doctest everything

[saraedum]

Currently, the following is not doctested and/or documented:

• [x] svgdigitizer (the package itself) (see #125)
• [x] svgdigitizer.cv (the module itself)
  • [x] Add link to workflow.md (see #87)
• [x] svgdigitizer.cv.CV (see #80)
  • [x] Add link to workflow.md (see #87)
• [x] svgdigitizer.cv.CV.axis_properties (see #80)
• [x] svgdigitizer.cv.CV.x_label (see #80)
• [x] svgdigitizer.cv.CV.df
  • [x] Implemented for a simple svg file (see #80)
• [x] svgdigitizer.cv.CV._add_U_axis() (see #80)
• [x] svgdigitizer.cv.CV._add_I_axis() (see #80)
• [x] svgdigitizer.cv.CV._add_time_axis() (see #80)
• [x] svgdigitizer.cv.CV.plot() (see #78)
• [x] svgdigitizer.cv.CV.metadata (see #80)
• [x] svgdigitizer.__main__ (see #86)
• [x] svgdigitizer.__main__.cli() (see #102)
• [x] svgdigitizer.__main__.plot() (see #86)
• [x] svgdigitizer.__main__.digitize() (see #102)
• [x] svgdigitizer.__main__.cv() (see #102)
• [x] svgdigitizer.__main__.paginate() (see #102)
• [x] svgdigitizer.svgplot (the module itself) (see #102)
• [x] svgdigitizer.svgplot.SVGPlot.labeled_paths (see #102)
• [x] svgdigitizer.svg (the module itself) (see #102)
• [ ] svgdigitizer.svg.LabeledPath.path_points()
• [ ] svgdigitizer.svg.LabeledPath.points
• [ ] svgdigitizer.svg.LabeledPath.__repr__()
• [ ] svgdigitizer.svg.Text.__repr__()
• [ ] svgdigitizer.svg.Text.__str__()
• [ ] svgdigitizer.test.cli
• [x] svgdigitizer.test.cli.invoke() (see #86)
• [x] svgdigitizer.test.cli.TemporaryData() (see #86)
• [ ] svgdigitizer.test.cli.TemporaryData.__enter__()
• [ ] svgdigitizer.test.cli.TemporaryData.__exit__()

The following are not documented and doctested but that's Ok. The classes should be documented and doctested instead since this information does not show up in the documentation anywhere anyway:

• svgdigitizer.cv.CV.__init__()
• svgdigitizer.svgplot.SVGPlot.__init__()
• svgdigitizer.svg.SVG.__init__()
• svgdigitizer.svg.LabeledPaths.__init__()
• svgdigitizer.svg.LabeledPath.__init__()
• svgdigitizer.svg.Text.__init__()
• svgdigitizer.test.cli.TemporaryData.__init__()