New Feature: allow customizing the name of the strategy.

Using this option, you instantiate the strategy multiple times with
different configurations.

bump version to v0.32.1

Audience validation

Upd: Mention ADFS 2016 with NameIDFormatError. (node-saml#242)

* Upd: Mention ADFS 2016 with NameIDFormatError.

* Formatting

Use crypto.randomBytes for ID generation (node-saml#235)

* Use crypto.randomBytes for ID generation

Math.random is not cryptographically secure, and IDs generated with it could potentially be predicted. Use crypto.randomBytes instead.

Update dependencies to be current.

Also, update "license" field to be current syntax.

The old "licenses" structure is deprecated.
Reference: https://docs.npmjs.com/files/package.json

handle bad privateCert

trap exceptions thrown by signRequest which can occurr when an invalid
 privateCert is passed to the saml object. Instead of throwing an
 exception pass the error along via the supplied callback

added spec to check that the callback his hit with the error condtion when
  calling requestToUrl on the saml object

Merge pull request node-saml#202 from cjbarth/readme-badges

Add badges to readme

README: link to related sections and clarify decryptionCert docs

Before it wasn't clear whether `decryptionCert` referred to
`decryptionPvk` or the public cert it is paired with. Adding the word
"public" clarifies that.

README: link to related sections and clarify decryptionCert docs

Before it wasn't clear whether `decryptionCert` referred to
`decryptionPvk` or the public cert it is paired with. Adding the word
"public" clarifies that.