Fix for ALMA based on its original implementation

Fixes #373

Original implementation by ALMA authors can be seen here:
https://www.sierrachart.com/SupportBoard.php?PostID=231318#P231318

pandas_ta/overlap/alma.py

@@ -1,6 +1,7 @@
 # -*- coding: utf-8 -*-
 from numpy import exp as npExp
 from numpy import nan as npNaN
+from math import floor
 from pandas import Series
 from pandas_ta.utils import get_offset, verify_series
 
@@ -17,7 +18,7 @@ def alma(close, length=None, sigma=None, distribution_offset=None, offset=None,
     if close is None: return
 
     # Pre-Calculations
-    m = distribution_offset * (length - 1)
+    m = floor(distribution_offset * (length - 1))
     s = length / sigma
     wtd = list(range(length))
     for i in range(0, length):