Do not capture 'filename'

phpmd resolves all paths to 'real' paths and uses such 'real' paths in the
reports. Since we cannot map such a 'real' path back to a 'user' path, we MUST
not capture these filename.

Fixes #21

linter.py

@@ -4,7 +4,10 @@
 class Phpmd(Linter):
     cmd = ('phpmd', '${temp_file}', 'text')
     regex = (
-        r'(?P<filename>.+):(?P<line>\d+)'
+        # For now, do *NOT* capture 'filename' since phpmd reports 'real'
+        # paths, and Sublime and SL cannot map such paths to the original
+        # `view.file_name()`.
+        r'(?P<filename_>.+):(?P<line>\d+)'
         r'\s*(?P<message>.+)$'
     )
     on_stderr = None  # handle stderr via regex