Update README.rst

`make` alone doesn't build the examples.
Merge pull request #44 from derekchiang/patch-1

Update README.rst
Fix build related to task::spawn_* functions deletion.
Merge pull request #45 from KokaKiwi/master

Fix build related to task::spawn_* functions deletion.
Update upstream iterator method names.
Update upstream iterator method names in codegen.
Updates for upstream closure reform.
Stop using std::cell (no longer necessary).