Allow to obtain instance without passing an Activity

Added getInstance() method.
Added initialize(Activity activity) method.
Merge pull request #37 from MateuszMlodawski/pr-instance

Allow to obtain instance without passing an Activity
Update README.md
Invite listener receives request id on complete

Invite listener onComplete method has an extra param for request id
generated by facebook. This id is needed to be stored by the client app
in most cases
Delete request added

deleteRequest method to enable deletion of facebook requests by client.
See
https://developers.facebook.com/docs/android/app-link-requests/#step3
for details of the need.
Fix bunch of potential NPEs. Added some comments. Fixed typos.
Now that the library can be started without an Activity/Context, care has to be taken so it doesn't attempt to use a null context.
Missing bracket. o.O
Fix incorrect listener that I accidentally inverted.
And finally restoring the right logic when the opened token has been updated.
I should get some rest
Fix 2 typos in the comments.
Getting apprequests added

Added me/apprequests that retrieves a JSONArray of pending requests. One
can list them in client side or just delete them as needed.
Added postScore for Scores API

In games, scores can be posted using this function.
Also added code documentation for deleteRequest.
Merge pull request #39 from koraybalci/master

Invite listener receives request id on complete
Merge pull request #40 from Gryzor/master

Fix bunch of potential NPEs. Added some comments. Fixed typos. Remove duplicated if statement.
update invite example after changes in commit
23f8b420778d8e99e9a7c16f9a2f9b81c78f4e96
typos
Getting scores added

We can get scores using the getScores function.
Merge pull request #41 from koraybalci/master

Getting scores added
Merge branch 'master' of
https://github.com/sromku/android-simple-facebook

Conflicts:
	Simple Facebook/src/com/sromku/simple/fb/SimpleFacebook.java