travis: Add back line length enforcement.

.travis.yml

@@ -14,3 +14,9 @@ script:
     # See this wiki page for why we're disabling these errors.
     # https://github.com/dylanaraps/neofetch/wiki/Shellcheck-Exclusions
     - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then shellcheck neofetch -e SC1090,SC2009,SC2012,SC2016,SC2034,SC2128,SC2153,SC2154,SC2178,SC2010,SC1004,SC1091,SC1117; fi
+    # The if statement is here to invert the exit code from grep.
+    # grep normally errors if no match is found but we want the opposite.
+    # We invert it so grep fails if a match is found.
+    # Check for lines longer than 100 chars.
+    # There are 3 lines that must be longer than 100 chars.
+    - if (("$(grep '.\{101\}' neofetch | wc -l)" > 3)); then (exit 1); else (exit 0); fi