Refs #1224 -- try to purge PyPI after new tarball is uploaded

Also reuse an HTTP connection for stuff
line length
Remove curve parameter from OpenSSL EC keys
Rename some ctx vars to ec_cdata
Move _ec_key_curve_sn to openssl/ec.py
fix links to ECWithNumbers classes in changelog
Merge pull request #1365 from reaperhulk/fix-ecnumbers-changelog

fix links to ECWithNumbers classes in changelog
Added an explanatory comment.
Merge pull request #1364 from public/remove-curve

Remove the curve parameter from OpenSSL EC keys
Merge pull request #1359 from alex/purge-pypi

Refs #1224 -- try to purge PyPI after new tarball is uploaded
Work around for side effects in setup.py script

Disables setup_requires and related magic for setup.py commands
clean, egg_info and sdist and the options --version and --help.

See also https://github.com/pyca/cryptography/issues/1253
Make sys.argv an argument of keywords_with_side_effects()
Change nested dictionary literal to match house style
PEP-8 fixes pointed out by Travis CI
Replace commands that depend on setup_requires with no-op that raises error
Bug fix for implementation of dummy commands

Pointed out by Jenkins:
https://jenkins.cryptography.io/job/cryptography-pr-experimental/2163/
Bullet proof (?) detection of arguments that don't need setup_requires
Simplify dummy commands (fix inheritance, remove finalize_options())
Fix for keywords_with_side_effects() (compatibility with pip metadata discovery)

Fixes a bug in 9e34c14b344f49d0721edc79d14ea5fc9c067d07 as described in
https://github.com/pyca/cryptography/pull/1257#issuecomment-48855243
Fix PEP-8 violations