Wrap title posterior values onto new line

[taylorbell57]

Currently, the median and +/- 1-sigma intervals for each corner plot 1D histogram are generated by:

corner.py/src/corner/core.py

Lines 270 to 272 in fa7e5c2

	# Add in the column name if it's given.
	if titles is not None:
	title = "{0} = {1}".format(titles[i], title)

Unless the font size is set to be very small (basically unreadably so), this results in plot titles that are far too wide to fit above the 1D histograms. However, if one tweaks that code block in this way:

 # Add in the column name if it's given. 
 if titles is not None: 
     title = "{0} =\\n{1}".format(titles[i], title) 

then the posterior intervals are pushed onto a new line and the titles fit far more nicely.