Remove itweet project for now

Broken upstream (a dependency doesn't exist) and still
waiting for a fix after more than a month.

index/itweet.mk

@@ -1,7 +0,0 @@
-PACKAGES += itweet
-pkg_itweet_name = itweet
-pkg_itweet_description = Twitter Stream API on ibrowse
-pkg_itweet_homepage = http://inaka.github.com/itweet/
-pkg_itweet_fetch = git
-pkg_itweet_repo = https://github.com/inaka/itweet
-pkg_itweet_commit = v2.0