Do not quote embedded slashes for public / signed URLs

[tseaver]

Closes #3809.

As noted on that issue, the public_url and generate_signed_url methods use the XML endpoints, which allow for / expect the slash not to be quoted. All other methods use the JSON endpoints, which require quoting the embedded slashes.

[frankyn]

@tseaver, it looks like it's still failing. Did you update the PR given the last commit was back in Jan 8?

Required test coverage of 97% reached. Total coverage: 99.97%
================================== FAILURES ===================================
__________________ Test_Blob.test_public_url_with_non_ascii ___________________
Traceback (most recent call last):
  File "C:\projects\google-cloud-python\storage\tests\unit\test_blob.py", line 182, in test_public_url_with_non_ascii
    self.assertEqual(blob.public_url, expected_url)
  File "C:\projects\google-cloud-python\storage\google\cloud\storage\blob.py", line 247, in public_url
    quoted_name=quote(self.name))
  File "c:\python27\Lib\urllib.py", line 1298, in quote
    return ''.join(map(quoter, s))
KeyError: u'\u2603'
1 failed, 422 passed in 3.61 seconds

[frankyn]

@tseaver, I think it's a unicode issue given the following SO question.

Given that, the line could be updated with:

quoted_name=quote(self.name.encode('utf-8')))

[tseaver]

@frankyn Thanks for tracking that down!

[tseaver]

@frankyn I opened issue #4935 for the unrelated Bigtable system test flakiness, and restarted the build after cleaning out the orphaned instances. I plan to merge here later today unless you see a problem.