Fixed a few minor typos.
Replaced noop lines with comment.
Replaced invalid comma with semi. Added terminating semicolons.
Added support for sharp grid lines.

The HTML5 canvas uses sub-pixel rendering, meaning that 1px wide lines often end up being blurred across two physical pixels. Considering a vertical line, its 'x' position specifies the center of the line. Therefore it spans +/-0.5 pixels from that point. Bam. Blurriness.

The solution is to subtract (adding would also work) 0.5 to the calculated x/y positions for vertical/horizontal lines respectively.

This patch does not change the default behaviour.

This problem is visible before this patch too, where the topmost and bottommost lines are 1px thick, while others are 2px thick.
Added an example with some control inputs.

A checkbox allows toggling the use of sharp grid lines.

Two other checkboxes allow toggling the max/min y-values, following a recent question on the mailing list.

This example also simulates data arriving at infrequet intervals.
Fixed per-frame-render warning in Firefox when series fillStyle undefined.

If a series does not specify a fillStyle, Firefox logs a warning each frame render:

> canvas: an attempt to set strokeStyle or fillStyle to a value that is neither a string, a CanvasGradient, or a CanvasPattern was ignored. @ http://localhost:8080/smoothie.js:301

This change fixes the issue by only setting the canvasContext.fillStyle property when seriesOptions.fillStyle is defined.
Merge pull request #29 from drewnoakes/feature/sharp-grid-lines

Option for sharp grid lines, and a few minor things