use raw string literal (#316)

addresses `DeprecationWarning: invalid escape sequence \w`

Author: robin-wayve

pyntcloud/io/pcd.py

@@ -23,7 +23,7 @@ def parse_header(lines):
     for ln in lines:
         if ln.startswith('#') or len(ln) < 2:
             continue
-        match = re.match('(\w+)\s+([\w\s\.]+)', ln)
+        match = re.match(r'(\w+)\s+([\w\s\.]+)', ln)
         if not match:
             warnings.warn("warning: can't understand line: %s" % ln)
             continue