Merge pull request #288 from joneshf/master

Add a couple Either/Maybe tests.
Fix #285
Release notes
Improve instance propagation #272
Release notes
Remove runtime type checks #93
Release notes
Improve some error messages #289 #290
Add --codegen option to support separate compilation
Release notes
Revert "Remove runtime type checks #93"

This reverts commit f34cf92aa8356754ae32874fac10aafe02b855c9.

Conflicts:
	psc/Main.hs
	psci/Main.hs
	src/Language/PureScript/Options.hs
Fix #292
Added on.