main.go: new import of go/exact and go/types
updated for new go/types API

Only updated to the point that everything
compiles, and examples appear to work correctly.

3 FIXMEs are left in code.
Cleaned up line 430 FIXME

Using name (package name) as first arg to context.Check
Resolved line 201 FIXME

Using package name of first parsed file as first argument
to context.Check
Merge pull request #19 from cookieo9/patch-1

Fix for API and URL update to go.exp