Adding .gitignore and disclaimer note in README

.gitignore

@@ -0,0 +1,51 @@
+*.pyc
+.waf*
+src/NDNabstraction
+build/
+doc/html/
+doc/latex/
+\.rej$
+\.orig$
+\.o$
+~$
+^build-dir
+^build
+^testpy-output
+^doc/html
+^doc/latex
+.lock-wscript
+doc/ns3-object.txt
+doc/introspected-doxygen.h
+.lock-waf_darwin_build
+.lock-waf_linux2_build
+.lock-waf_cygwin_build
+.lock-waf_freebsd7_build
+.lock-waf_freebsd8_build
+.lock-waf_freebsd9_build
+.waf
+^doc/introspected-doxygen\.h$
+.*\.py[co]$
+\.pcap$
+\.mob$
+\.routes$
+^doc/manual/build
+^doc/tutorial/build
+^doc/testing/build
+^doc/models/build
+^doc/models/source-temp
+^doc/manual/figures/.*eps
+^doc/manual/figures/.*pdf
+^doc/manual/figures/.*png
+^bindings/python/pybindgen/
+ms_print.*
+massif.*
+\.patch$
+\.diff$
+\.tr$
+\#[^\#/]+\#$
+.lock-wscript
+.lock-wafbuild
+src/ndnSIM
+configure
+toggle
+

README

@@ -1,3 +1,9 @@
+Note:
+
+This is a custom and unsupported fork of NS-3 simulator (http://www.nsnam.org/).
+
+**The code in this repository is frequently rebased on top of the latest ns-3-dev branch** 
+
 
     The Network Simulator, Version 3
     --------------------------------