v0.2.0

• Use a StrMap String for child process environments in spawn, in order to ensure environment variable values are strings
• Allow inheritance of parent process environment by passing Nothing to the env parameter
• Use an opaque data type for ChildProcess values
• Use Int instead of Number where applicable (eg, gid, uid, pid)
• Require Eff for reading mutable state of a ChildProcess
• Simplify effects; now, we just have cp :: CHILD_PROCESS for spawning and communicating with child processes
• Use a sum type to allow more flexibility with what to do with standard IO streams / file descriptors in the child process after spawning
• Fix a bug where callbacks in onExit and onClose did not get called
• Add a ChildProcessExit type with information about how a child process exited
• Fix warnings
• Update dependencies: purescript-node-streams -> ~0.3.0

See joneshf/purescript-node-child-process#2 for the rationale behind many of these changes.