Add gcc 8.2.1 and update 8.0.2

Author: tmcgilchrist

.travis.yml

@@ -3,7 +3,8 @@
 # The following enables several GHC versions to be tested; often it's enough to test only against the last release in a major GHC version. Feel free to omit lines listings versions you don't need/want testing for.
 env:
  - CABALVER=1.22 GHCVER=7.10.3
- - CABALVER=1.24 GHCVER=8.0.1
+ - CABALVER=1.24 GHCVER=8.0.2
+ - CABALVER=2.0 GHCVER=8.2.1
 
 # Note: the distinction between `before_install` and `install` is not important.
 before_install: