Fix minor typos/errors in iOS-push tutorial

From Deepali:

• In chapter 3, unified push server, I couldn't find the location of the pushee server and install instructions. A pointer to this would be helpful: https://github.com/matzew/pushee

• In the Readme link above, it was not obvious to me that you are referring to JBoss AS server, please mention that.
  "./bin/standalone.sh -b 0.0.0.0 -c standalone-full.xml"

• Many of the referenced urls need to be fixed, example:
  currently, reference are relative:
  http://aerogear.org/docs/guides/aerogear-push-ios/iOS-app/:http://cocoapods.org/
  instead of:
  http://cocoapods.org/

• I had some confusion about which id to use in chapter 5, send push. Using the same name (PushApplicationID) in register and send may help.