plot_taylor errors

[vascoamaralgrilo]

Good afternoon,

I believe there are a few typos in plot_taylor from orbit_plots:

0- In lines 246 and 248, "thrust" should be "u".
1- Before the cycle which starts at line 295, there should be "r = r0", "v=v0" and "m=m0".
2- In line 299, "r0", "v0" and "m0" should be "r", "v" and "m", respectively.

Kind regards,

Vasco

[pabloem]

This is also fixed by #137