Remove the manual ShellCheck install proecss on Travis CI

.travis.yml

@@ -23,7 +23,6 @@ before_install:
   - curl --version
   - wget --version
 install:
-  - if [ -n "${SHELLCHECK-}" ]; then cabal update && cabal install ShellCheck && shellcheck --version ; fi
   - if [ -z "${SHELLCHECK-}" ]; then nvm install node && npm install && npm prune && npm ls urchin doctoc; fi
   - '[ -z "$WITHOUT_CURL" ] || sudo apt-get remove curl -y'
 script:
@@ -38,7 +37,7 @@ env:
   global:
     - CXX=g++-4.8
     - CC=gcc-4.8
-    - PATH="~/.cabal/bin/:$(echo $PATH | sed 's/::/:/')"
+    - PATH="$(echo $PATH | sed 's/::/:/')"
     - NVM_DIR="${TRAVIS_BUILD_DIR}"
   matrix:
     - MAKE_RELEASE=true