Fixes const iteration for chain()

Fixes ryanhaining#65

Merge pull request ryanhaining#45 from nvander1/remove_std_iterator

Remove use of std::iterator

Removes this-> in starmap::iterator functions.

clang was getting confused by them, I don't know why.

Merge branch 'master' of https://github.com/ryanhaining/cppitertools

removes noexcept from accum iterator move