DOC: Add See Also links and Example graphs to filter design *ord functions

[endolith]

Also fixed a typo in a printed warning. Should that be converted to a raised warning or exception?

[coveralls]

Coverage remained the same when pulling a09d8dc on endolith:patch-3 into 6b6b41a on scipy:master.

[rgommers]

Remove the comma after cheb2ord, otherwise the doc build crashes

[rgommers]

For the rest this looks good to me. Nice figures.

[endolith]

Ok, fixed both of those.

[coveralls]

Coverage remained the same when pulling 19d71f5 on endolith:patch-3 into 6b6b41a on scipy:master.

[rgommers]

Thanks, merging

[endolith]

It looks like I screwed something up. The images show up on http://docs.scipy.org/doc/scipy-dev/reference/generated/scipy.signal.ellipord.html and http://docs.scipy.org/doc/scipy-dev/reference/generated/scipy.signal.buttord.html, but not on http://docs.scipy.org/doc/scipy-dev/reference/generated/scipy.signal.cheb1ord.html and http://docs.scipy.org/doc/scipy-dev/reference/generated/scipy.signal.cheb2ord.html Any idea why?

Also the lines like

butter, cheby1, cheby2, ellip, bessel : Filter design using order and
                                        critical points

are not working. I guess they can't have commas in them?

I could reword it to

butter : Filter design using order and critical points
cheby1, cheby2, ellip, bessel

also should have added an example/graph for iirdesign.

[rgommers]

If you just paste the example into a clean IPython shell you'll see where it fails.The issue should be that you're using pi instead of np.pi. I failed to recheck the doc build after your last commit, my bad.

[rgommers]

As for See Also, I think it's either a list of functions or a single function with a description behind it.

[endolith]

I tried to add the fixes to the same patch, but they're not showing up here, maybe because it's already been merged?

They are visible here: endolith@137ace8

[rgommers]

You indeed can't add commits to a PR that has been merged already. I'll cherry-pick and push that commit (after double checking it).

[rgommers]

Pushed doc fix commit in 28f9d10