Adding contributing instructions
Converting array to []
Changing minimum php version to 5.4
Removing 5.3 build from Travis
Merge pull request #11 from gabrielsch/converting-short-array

Using short-array syntax and requiring PHP 5.4+
Changing constants to string so methods wont broke as #12 reports
Merge branch 'develop' of github.com:PHPSC/pagseguro into develop
Merge branch 'release/1.0.0alpha6'