transformation name with spaces causes 400 error

Making a call to get transformations, some of them come back with spaces in the name like this:

```
{u'allowed_for_strict': False,
u'name': u'fl_progressive,t_primary/t_t_primary@2x jpg.t_primary@2x jpg.display@2x',
u'used': False},
```

Now trying to use that (ignoring issue #41 for now), generates a 400 server error:

```
In [10]: name = 'fl_progressive,t_primary/t_t_primary@2x jpg.t_primary@2x jpg.display@2x'

In [11]: cloudinary.api.transformation(name)
---------------------------------------------------------------------------
GeneralError Traceback (most recent call last)
in ()
----> 1 cloudinary.api.transformation(name)

.../venv/lib/python2.7/site-packages/cloudinary/api.pyc in transformation(transformation, **options)
129 def transformation(transformation, **options):
130 uri = ["transformations", transformation_string(transformation)]
--> 131 return call_api("get", uri, only(options, "max_results"), **options)
132
133 def delete_transformation(transformation, **options):

.../venv/lib/python2.7/site-packages/cloudinary/api.pyc in call_api(method, uri, params, **options)
225 # Error is parsing json
226 e = sys.exc_info()[1]
--> 227 raise GeneralError("Error parsing server response (%d) - %s. Got - %s" % (response.code, body, e))
228
229 if "error" in result:

GeneralError: Error parsing server response (400) - . Got - No JSON object could be decoded
```

The fix it seems is to renencode the name using url encoding:

```
In [12]: name = 'fl_progressive,t_primary/t_t_primary@2x%20jpg.t_primary@2x%20jpg.display@2x'

In [13]: cloudinary.api.transformation(name)
Out[13]:
{u'allowed_for_strict': False,
u'derived': [],
u'info': [{u'flags': [u'progressive'], u'transformation': [u'primary']},
{u'transformation': [u't_primary@2x jpg', u'display@2x']}],
u'name': u'fl_progressive,t_primary/t_t_primary@2x jpg.t_primary@2x jpg.display@2x',
u'used': False}
```