Incorrect error reports in http downloads.

Note in the below session:

1. server log says http support disabled. This is not correct.
2. The error message says the index file X could not be parsed, but X is not the index file.

In [2]: X = tc.SFrame("http://mlr.cs.umass.edu/ml/machine-learning-databases/abalone/abalone.data")
Downloading http://mlr.cs.umass.edu/ml/machine-learning-databases/abalone/abalone.data/dir_archive.ini to /var/tmp/turicreate-hoytak/24918/7c27c29f-2d35-4767-9847-aed3f438af54.ini
Failed to download http://mlr.cs.umass.edu/ml/machine-learning-databases/abalone/abalone.data/dir_archive.ini: HTTP response code said error
Downloading http://mlr.cs.umass.edu/ml/machine-learning-databases/abalone/abalone.data to /var/tmp/turicreate-hoytak/24918/98aa046f-60d4-4227-9b89-b3098ff3c5af.data
---------------------------------------------------------------------------
RuntimeError                              Traceback (most recent call last)
<ipython-input-2-4ad5bb7a9ff9> in <module>()
----> 1 X = tc.SFrame("http://mlr.cs.umass.edu/ml/machine-learning-databases/abalone/abalone.data")

/Users/hoytak/venv/lib/python2.7/site-packages/turicreate/data_structures/sframe.pyc in __init__(self, data, format, _proxy)
    812                     pass
    813                 else:
--> 814                     raise ValueError('Unknown input type: ' + format)
    815 
    816     @staticmethod

/Users/hoytak/venv/lib/python2.7/site-packages/turicreate/cython/context.pyc in __exit__(self, exc_type, exc_value, traceback)
     47             if not self.show_cython_trace:
     48                 # To hide cython trace, we re-raise from here
---> 49                 raise exc_type(exc_value)
     50             else:
     51                 # To show the full trace, we do nothing and let exception propagate

RuntimeError: Unable to parse frame index file http://mlr.cs.umass.edu/ml/machine-learning-databases/abalone/abalone.data

In [6]: !cat /tmp/turicreate_server_1543438749.log.0
1543438757 : PROGRESS: (download_url:43): Downloading http://mlr.cs.umass.edu/ml/machine-learning-databases/abalone/abalone.data/dir_archive.ini to /var/folders/v5/n05q0v_55ln_6gng2f_476_r0000gn/T/turicreate-hoytak/24838/1e71bfdd-6a7b-4aed-b92b-596842f9231b.ini
1543438757 : PROGRESS: (download_url:59): Failed to download http://mlr.cs.umass.edu/ml/machine-learning-databases/abalone/abalone.data/dir_archive.ini: HTTP response code said error
1543438757 : ERROR:    (operator():64): Not implemented: compiled without support for http(s):// URLs.
1543438757 : ERROR:    (operator():27): Cannot open http://mlr.cs.umass.edu/ml/machine-learning-databases/abalone/abalone.data/dir_archive.ini for read. Not implemented: compiled without support for http(s):// URLs.
1543438757 : PROGRESS: (download_url:43): Downloading http://mlr.cs.umass.edu/ml/machine-learning-databases/abalone/abalone.data to /var/folders/v5/n05q0v_55ln_6gng2f_476_r0000gn/T/turicreate-hoytak/24838/59cf93c1-c3da-4214-819d-4779ca13484c.data
1543438758 : ERROR:    (operator():32): Unable to parse frame index file http://mlr.cs.umass.edu/ml/machine-learning-databases/abalone/abalone.data