Take care of the next letter when A/a is replaced by l

Fix #304.

cairosvg/path.py

@@ -186,7 +186,14 @@ def path(surface, node):
 
  # rx=0 or ry=0 means straight line
  if not rx or not ry:
- string = 'l {} {} {}'.format(x3, y3, string)
+ if string and string[0] not in PATH_LETTERS:
+ # As we replace the current operation by l, we must be sure
+ # that the next letter is set to the real current letter (a
+ # or A) in case it’s omitted
+ next_letter = '{} '.format(letter)
+ else:
+ next_letter = ''
+ string = 'l {} {} {}{}'.format(x3, y3, next_letter, string)
  continue
 
  radii_ratio = ry / rx