Bump requests from 2.13.0 to 2.19.1

[dependabot-preview]

Bumps requests from 2.13.0 to 2.19.1.

Changelog

Sourced from requests's changelog.

2.19.1 (2018-06-14)
+++++++++++++++++++

Bugfixes

• Fixed issue where status_codes.py's init function failed trying to append to
  a __doc__ value of None.

2.19.0 (2018-06-12)
+++++++++++++++++++

Improvements

• Warn user about possible slowdown when using cryptography version < 1.3.4
• Check for invalid host in proxy URL, before forwarding request to adapter.
• Fragments are now properly maintained across redirects. (RFC7231 7.1.2)
• Removed use of cgi module to expedite library load time.
• Added support for SHA-256 and SHA-512 digest auth algorithms.
• Minor performance improvement to Request.content.
• Migrate to using collections.abc for 3.7 compatibility.

Bugfixes

• Parsing empty Link headers with parse_header_links() no longer return one bogus entry.
• Fixed issue where loading the default certificate bundle from a zip archive
  would raise an IOError.
• Fixed issue with unexpected ImportError on windows system which do not support winreg module.
• DNS resolution in proxy bypass no longer includes the username and password in
  the request. This also fixes the issue of DNS queries failing on macOS.
• Properly normalize adapter prefixes for url comparison.
• Passing None as a file pointer to the files param no longer raises an exception.
• Calling copy on a RequestsCookieJar will now preserve the cookie policy correctly.

Dependencies

• We now support idna v2.7.
• We now support urllib3 v1.23.

2.18.4 (2017-08-15)
+++++++++++++++++++

Improvements

• Error messages for invalid headers now include the header name for easier debugging

Dependencies

• We now support idna v2.6.

2.18.3 (2017-08-02)

... (truncated)

Commits

• 883caaf v2.19.1
• 2530323 Merge pull request #4683 from martindurant/docstrings_for_optimize
• 8031ec7 Do not alter status_codes docstring if it is None
• 991e8b7 v2.19.0
• 7e297ed Separate collections from collections.abc
• 10915e3 Add a public method to get the cookie policy
• ace0c20 Add cookie policy related tests
• 3ef4927 Copy cookie policy when copying a CookieJar
• d1aeb7e Merge pull request #4672 from requests/remove_2.6_refs
• de64f0f port pyopenssl fix from urllib3
• Additional commits viewable in compare view

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[dependabot-preview]

Superseded by #19.