Fix issue with points on multiple line series

The line series were only selecting all circles on the chart, then
comparing against their own data. Now, we use a classname for the line
points, which is unique for the line (assuming names are unique).

This lets us have 2 line series on a chart, and configure whether they
show or hide points independent of each other.
Update changelog
Merge branch 'upstream' into feature/two-line-points

Conflicts:
	Changelog.txt
Remove spaces from CSS classname

Applies the same fix as shortClassName did, replacing spaces with "_"
Factor out common string-cleaning

Moves the regex string for removing non-alphanumeric characters into its
own utility method.
Merge pull request #178 from tpkelly/feature/two-line-points

Fix issue with points on multiple line series