util.py: quote failed command for readability
Introduce 'retry' option

Add a 'retry' option which allows to configure how many
retries pip should make before giving up on HTTP request.

When the retries count is specified by user, its value is
passed to HTTPAdapter from requests which handles all
the underlying operations.
Remove bootstrap function, simplify __main__
Docs -- fix typo
Merge pull request #1603 from r3m0t/patch-1

Docs -- fix typo
pkg exclusions for pip list/freeze
Merge pull request #1598 from Ivoz/rmbootstrap

Remove bootstrap function, simplify __main__
update python support in classifiers
have setup.py long_description just be README.rst
update MANIFEST.in
Merge pull request #1609 from qwcode/readme

have setup.py long_description just be README.rst
fixes #1589
Merge pull request #1614 from evildmp/fix-1589-editable-docs

fixes #1589
Put a space around a comma for readability.
Merge pull request #1619 from alex/patch-2

Put a space around a comma for readability.
update changelog
Merge pull request #1606 from qwcode/stdlib_pkg_filter

stdlib pkg exclusions for pip list/freeze
fixes #1615
Merge pull request #1623 from dstufft/1615-docs-typos

fixes #1615
Merge pull request #1444 from novel/retries

Introduce 'retry' option