Added support for `exp` to README.
Borrowed much of the verbiage from [PyJWT's README](https://github.com/progrium/pyjwt/blob/90beaa320b6ca0a4765ace46b1355d9b2ebadf77/README.md).
Added tests for `exp` header support.
Borrowed tests from [PyJWT](https://github.com/progrium/pyjwt)
Need that default expiration to be futuristic..
Added support for `exp` header.
added @zshannon to list of contributors
bumped version to 1.1 now that we support `exp` claim
Merge pull request #45 from zshannon/feature-exp-support

Added support for `exp` claim