Merge tag '0.9.11' into develop

method rename + new method added
Merge branch 'develop' of github.com:wearearchitect/sharepoint-oauth-app-client into develop
feat(*): implemented getSPItems() method and removed getSPFiles()
feat(*): added debug option on the request() method
chore(*): updated request() method signature
feat(*): added getRaw() method
feat(*): create() and update() methods now support contents as string
Merge branch 'hotfix/0.9.14'
chore(*): no need to pass objects by reference since PHP takes care of that
chore(SPException): added getPreviousMessage() method
chore(SPSite): inject Guzzle HTTP client in the constructor + added static create() method + cleanups
chore(*): added PHPUnit as a dev requirement
chore(SPSite): added initial tests
chore(SPSite): variable renaming
chore(SPUser): extend SPObject + update class + add extra property support
chore(*): move common SharePoint object methods/properties to abstract SPObject class
chore(*): give the trait a more meaningful name
chore(SPSite): more flexible arguments in the create() method
chore(*): change properties visibility to protected
chore(*): change from trait to abstract class and remove interface