commoncrypto PBKDF2 support
update commoncrypto pbkdf2 with new naming
update changelog
Merge branch 'master' into pbkdf2-commoncrypto

* master:
  a bit more language work + changelog changes for pbkdf2hmac
  one more style fix
  a few typo fixes, capitalization, etc
  switch to private attributes in pbkdf2hmac
  expand docs to talk more about the purposes of KDFs
  update docs re: PBKDF2HMAC iterations
  add test for null char replacement
  Added installation section to index.rst
  called -> used
  quotes inside, diff examples
  Expose this method because probably someone will need it eventually
  fix spacing, remove versionadded since HashAlgorithm was in 0.1
  document HashAlgorithm
  Added canonical installation document with details about various platforms, fixes #519
  update docs for pbkdf2
  Add bindings for X509_REQ_get_extensions.
  add Konstantinos Koukopoulos to AUTHORS.rst
  review fixes
  doc updates based on review

Conflicts:
	docs/changelog.rst
simplify check for algorithm
simplify hmac supported and hash supported calls for commoncrypto
one more replacement
PBKDF2HMAC requires a PBKDF2HMACBackend provider.

I cannot be trusted with a pasteboard
Merge pull request #532 from reaperhulk/cc-make-supported-calls-more-better

CC make supported calls more better
Merge pull request #533 from reaperhulk/pbkdf2-docs-fix

PBKDF2HMAC requires a PBKDF2HMACBackend provider.
Merge pull request #531 from reaperhulk/pbkdf2-commoncrypto

PBKDF2HMAC (CommonCrypto)
Fixed up some backwards syntax in the docs
Merge pull request #534 from alex/docs-fixes

Fixed up some backwards syntax in the docs
PKCS#1 vectors

From ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/ and
ftp://ftp.rsa.com/pub/rsalabs/tmp/
Merge pull request #537 from public/pkcs1-vectors

PKCS#1 vectors
Fixes #539 -- document which interfaces a backend implements
Complete sentences.
Merge pull request #540 from alex/document-interfaces

Fixes #539 -- document which interfaces a backend implements
Handle multiple errors on the stack
Merge pull request #541 from public/fix-466

Handle multiple errors on the stack