Allow to specify tags for 'install' and 'install-cabal'

.travis.sh

@@ -25,10 +25,17 @@ edo ./ghcup -v rm -f 8.6.1
 
 # set GHC
 edo ./ghcup -v set 8.2.2
+edo ./ghcup -v rm -f 8.2.2
 
 # install default GHC
 edo ./ghcup -v install
 
+# install latest GHC
+edo ./ghcup -v install latest
+
+# FIXME: this might break from time to time depending on recommended GHC
+edo ./ghcup -v set 8.4.4
+
 export PATH="$HOME/.cabal/bin:$HOME/.ghcup/bin:$HOME/.local/bin:$PATH"
 edo mkdir -p "$HOME"/.local/bin