Merge pull request #174 from darioizzo/master

small docs update ... no warnin upon import

Author: darioizzo

pykep/orbit_plots/_plots.py

@@ -24,7 +24,7 @@ def plot_planet(plnt, t0=0, tf=None, N=60, units=1.0, color='k', alpha=1.0, s=40
 	ax = fig.add_subplot(projection='3d')
 	pl = pk.planet.jpl_lp('earth')
 	t_plot = pk.epoch(219)
-	ax = pk.orbit_plots.plot_planet(pl, ax = ax, color='b')
+	ax = pk.orbit_plots.plot_planet(pl, axes = ax, color='b')
     """
     from pykep import MU_SUN, SEC2DAY, epoch, AU, RAD2DEG
     from pykep.planet import keplerian

pykep/trajopt/_pl2pl_N_impulses.py

@@ -15,7 +15,7 @@ class pl2pl_N_impulses(object):
 
     ... in the units: [mjd2000, days] + [nd, nd, m/sec, nd] + [nd] + [mjd2000]
 
-    Each time-of-flight can be decoded as follows, T_n = T log(alpha_n) / \sum_i(log(alpha_i))
+    Each time-of-flight can be decoded as follows, T_n = T log(alpha_n) / \\sum_i(log(alpha_i))
 
     .. note::