Update README.md

pip is a preferred way to install 3rd party packages.
Merge pull request #49 from methane/patch-1

Update README.md
Merge pull request #47 from methane/python3

[python3] merge master and some cleanup
Support X509 pem cert and signature verification using PyCrypto.
Fix the test with PyCrytoVerifier.
Revert change of PyCryptoVerifier.verify() since current code turns out working.

	modified:   oauth2client/crypt.py
fix bytes-str conversion
use bytes literal
Merge pull request #51 from liujin-google/master

Support X509 pem cert and signature verification using PyCrypto.
Merge pull request #52 from nazo/python3

[python3]fix bytes-str conversion
Added error description to AccessTokenRefreshError

The JSON response returned can contain an "error_description" field that contains additional information about the error. If found, appending to the error message.
Merge pull request #53 from erickoledadevrel/errormessage

Added error description to AccessTokenRefreshError
Update a path in a test file.
Update all copyright lines.
Source cleanup (mostly lint), one missing rename.

This mostly cleans up a few lint errors, normalizes some formatting and import
order, etc. I'm not yet attempting to make things lint clean, just making some
progress.

I also fixed one error with a `simplejson` call that didn't get renamed.
One more copyright update.
Fix a test failure (mismatched error strings).
Better behavior around missing crypto dependencies.

Previously, if no crypto library was available, two top-level bindings in
oauth2client.client would never be created. This creates an awkward situation
for callers (who may now have `AttributeError` arising in unexpected places).

This fixes the issue by always creating the top-level bindings, and simply
raising an exception at runtime if no crypto library is available.

Note that we keep `HAS_CRYPTO` and `HAS_OPENSSL`. These values are part of the
public interface for this module, and apparently are used as such (cf
https://groups.google.com/forum/#!msg/google-api-python-client/aVU-fgTpXsc/JxS5vRtXWd8J).
Merge pull request #56 from craigcitro/better_crypt_error

Better behavior around missing crypto dependencies.
Update docs for 1.3 release.