Do not require matplotlib to be installed

pyzebra/xtal.py

@@ -1,11 +1,16 @@
 import math
 
 import numpy as np
-from matplotlib import pyplot as plt
 from scipy.optimize import curve_fit
 
 import pyzebra
 
+try:
+    from matplotlib import pyplot as plt
+except ImportError:
+    print("matplotlib is not available")
+
+
 
 def z4frgn(wave, ga, nu):
     """CALCULATES DIFFRACTION VECTOR IN LAB SYSTEM FROM GA AND NU