update indigo

* submodules/indigo 216a076...655d3cd (2):
  > Merge into master from pull request #160: OFConnectionManager: add assertions for clang static analyzer (https://github.com/floodlight/indigo/pull/160)
  > Merge into master from pull request #159: Optimize flowtable iteration (https://github.com/floodlight/indigo/pull/159)