This commit renames the various constructors of networking types to have a
`_std` suffix instead of a smorgasboard of other suffixes, canonicalizing on
`_std` as the suffix for constructors which take the libstd corresponding types.
In accordance with tokio-rs/tokio-rfcs#3, the executor functionality of
Tokio is being removed and will be relocated into futures-rs as a
"current thread" executor.
This PR removes task execution from the code base. As a temporary
mesure, all examples and tests are switched to using CpuPool.
Depends on #19.
