Implement fix-permissions verb.

- Recursively change ownership of ROS HOME to current user.
 - Fixes: https://github.com/ros-infrastructure/rosdep/issues/332
Actually it's just completely crazy:

```python
% python
Python 2.7.5 (default, Mar  9 2014, 22:15:05)
[GCC 4.2.1 Compatible Apple LLVM 5.0 (clang-500.0.68)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> a = "foo"
>>> b = "föö"
>>> b
'f\xc3\xb6\xc3\xb6'
>>> b = u"föö"
>>> b
u'f\xf6\xf6'
>>> str(a)
'foo'
>>> str(b)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
UnicodeEncodeError: 'ascii' codec can't encode characters in position 1-2: ordinal not in range(128)
>>> "%s" % a
'foo'
>>> "%s" % b
u'f\xf6\xf6'
>>> "%s" % a
'foo'
>>> "%s" % b
u'f\xf6\xf6'
>>> "{0}".format(a)
'foo'
>>> "{0}".format(b)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
UnicodeEncodeError: 'ascii' codec can't encode characters in position 1-2: ordinal not in range(128)
>>> b = "föö"
>>> "{0}".format(b)
'f\xc3\xb6\xc3\xb6'
>>> u"{0}".format(b)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 1: ordinal not in range(128)
>>> b = u"föö"
>>> u"{0}".format(b)
u'f\xf6\xf6'
```

Don't change this.