TODO

[x] license (LGPL)
[x] fucking name this thing
[x] fastspawn-bm should take iterations and memsize arguments
[x] high level Grit::Process like class (string based) (tmm1)
[x] add FD => '/path/to/file' (all variations) (rtomayko)
[x] raise exception on unhandled options
[x] benchmarks in README (tmm1)
[x] POSIX::Spawn::spawn usage examples in README
[x] POSIX::Spawn#pspawn should be just #spawn
[x] :err => :out case -- currently closing out after dup2'ing
[x] POSIX::Spawn::Process.new should have same method signature as Process::spawn
[x] POSIX::Spawn::Process renamed to POSIX::Spawn::Child
[x] Better POSIX::Spawn#spawn comment docs
[x] POSIX::Spawn::Child usage examples in README


[ ] popen* interfaces
[x] system interface
[x] ` interface
[ ] jruby Grit::Process stuff
[ ] make :vfork an option to Spawn#spawn
[ ] check all posix_spawn_* function call return values
[ ] POSIX::Spawn as ::Spawn? (maybe, we'll see)