Added more drawing options and line tooltips

drawDots, drawLegend and addTooltips can now be passed in as options to
a line chart. Also added addLineTooltips option that will display
interpolated data when hovering over a line. (The goal was to make it
possible to display lots of data in a graph by enabling line tooltips
and disabling dots)
Changed 'mouseeover' to 'mousemove' on lineTooltip

Changed 'mouseeover' to 'mousemove' on lineTooltips so that values will
update if the user hovers along a line
Changed mouseover to mousemove for path and interpolation bug fix.

Updated lineGroup to listen on mousemove instead of mouseover. Also
fixed a bug with viewing tooltip on last datapoint in a line.
Fix for interpolation on left most datapoint
Refactored line datum interpolation, updated tests

Line datum interpolation is now just based on the mouse coordinates and
the axes. This turned out to be simpler and more accurate than the
previous method. Added tests for new default options and functionality.
Also added ‘hoverMove’ method to fakeMouse for testing ‘mousemove’
event.
Updated tooltipMode

Got rid of addLineTooltips and addTooltips in favor of toolTipMode.
tooltipMode now takes ‘none’, ‘dots’, ‘lines’ or ‘both’. The default is
‘dots’. addTooltips = false now sets toolTipMode to ‘none’.
Updated distribution files and removed addTooltips

Rebuilt dist/ files. options no longer uses addTooltips or tests for it.
Fixed drawLegend call order

Fixed an error where drawLegend was being called out of order
Merge pull request #80 from domrein/master

Updates for drawing line chart with lots of data points.