Fix regex as the : after the column is optional

Fixes SublimeLinter/SublimeLinter#1847
Closes #17

Output from pyflakes can be

```
<stdin>:1044:12 undefined name 'settingss'
<stdin>:34:45: invalid syntax
```

t.i. the `:` after the column is optional.  In the latter case
`filename` overmatched ("not lazy") to "<stdin>:34".

linter.py

@@ -5,7 +5,7 @@
 class Pyflakes(PythonLinter):
     cmd = 'pyflakes'
     regex = r'''(?x)
-        ^(?P<filename>.+):(?P<line>\d+):((?P<col>\d+):?)?\s
+        ^(?P<filename>.+?):(?P<line>\d+):((?P<col>\d+):?)?\s
 
         # The rest of the line is the error message.
         # Within that, capture anything within single quotes as `near`.