initial implementation of water fraction diagnostic routine
fix lagrange multiplier in CTDCast.water_fraction

...and add a simple test

also enforce output of kronecker product to be "csr" for speed
add experimental d3 plotting built on mpld3
revamp TS plotting functions - now a cleaner interface
fix color cycling
return fraction arrays the same shape as cast
Merge branch 'new_plot_ts' of github.com:njwilson23/narwhal into new_plot_ts

Conflicts:
	narwhal/plotting.py