* Removed unused `i`.

* Passed `legendItem` directly.

* Checked that all jasmine and image tests still pass.

* Set tspan.line's x in the callback to convertToSpans, otherwise they
  won't be set in the first render.

* Checked all jasmine and image tests still pass.

* Ensure the position of the `tspan.line`s is set before computing the
  legend dimensions and expanding the margins.

* The baseline image for `pseudo_html.json` needed updating because it
  has a multi-line legend.

* This change not only improves drawing performance, but it will also
  allows for `drawTexts` to be moved to `styles.js`.

* Checked all jasmine and image tests still pass.

* Moved the placing of legend groups to `computeLegendDimensions` so
  that they are handled along with the placing of legend traces.

* This change is a preliminary step to implement horizontal legends.

* Checked all jasmine and image tests still pass.

* Added `legend_horizontal.json` (a mock with a horizontal legend
  without groups).

* Added `legend_horizontal_groups.json` (a mock with a grouped
  horizontal legend).

* Used `selection.call()` to invoke drawTexts, setupTraceToggle and
  computeTextDimentions.

* Removed legendItem from the function signatures of drawTexts,
  setupTraceToggle and computeTextDimensions.

* Position horizontal legends on the bottom left, unless a range slider
  is present.

* If a range slider is present, position the horizontal legend on the
  top left.