getExpirationTimestamp now returns int value

AWS UrlSigner accept both string and int as expires parameter, but it actually creates problems.

Using AWS UrlSigner instead of CloudFrontClient

v0.1.4

Used UrlSigner instead of CloudFrontClient etc

$expiration has a default whatever is the accessing method (helper, facade)

v0.1.3

Fixed README

sign() helper $expiration parameter now has a default

v0.1.2

Added $expiration default to sign() helper

Added sign() helper

v0.1.1

Added sign() helper

Initial release

v0.1.0

Added README