Fix the retrieval of the latest compiler version tag (#122)

See https://discourse.purescript.org/t/new-404-ci-failures-in-core-libraries/1225.

Author: kl0tl

.travis.yml

@@ -5,8 +5,8 @@ node_js: stable
 env:
   - PATH=$HOME/purescript:$PATH
 install:
-  - TAG=$(wget -q -O - https://github.com/purescript/purescript/releases/latest --server-response --max-redirect 0 2>&1 | sed -n -e 's/.*Location:.*tag\///p')
-  - wget -O $HOME/purescript.tar.gz https://github.com/purescript/purescript/releases/download/$TAG/linux64.tar.gz
+  - TAG=$(basename $(curl --location --silent --output /dev/null -w %{url_effective} https://github.com/purescript/purescript/releases/latest))
+  - curl --location --output $HOME/purescript.tar.gz https://github.com/purescript/purescript/releases/download/$TAG/linux64.tar.gz
   - tar -xvf $HOME/purescript.tar.gz -C $HOME/
   - chmod a+x $HOME/purescript
   - npm install -g bower