implement path_effects for Line2D objects

[leejjoon]

This patch implements path_effects for Line2D objects.

Here is a related request on the mailing list

http://www.mail-archive.com/matplotlib-users@lists.sourceforge.net/msg22954.html

The current change modifies the Line2D class to take a single path_effects argument. However, there are two paths involved with a single Line2D instance.

• a path for the line
• a path for the marker edge & face

And currently, same path_effects is applied to both paths.
I'm not sure if there is a need to apply separate path_effects for those two.
We may need an optional argument (e.g., marker_path_effects).

[jdh2358]

I would like to test this PR, but it would be easier if there were some example or test. Could you add something simple?

[dmcdougall]

I tried this and got a nice shadow on the legend! Works fine for me on Mac OS X 10.7, Python 2.7.2 and PDF backend. When I checked out your code I had to fiddle with a conflict in lines.py, just to let you know. Otherwise this looks fine.

[mdboom]

Sorry this got "dropped" for so long. I think this needs a regression test (do we have any for path effects yet? Maybe that warrants a new test directory). Other than that and the other comments above, I think this is probably ready to merge.

[mdboom]

Also -- can you rebase against the current master?

[jdh2358]

I second the request to see this rebased against master so we can move this PR forward

[leejjoon]

The rebased version of this pull request is available at #1015. I am closing this PR.