Add Travis CI check for whitespace at the ends of lines. (#1477)

Author: godbyk

.travis.yml

@@ -7,6 +7,7 @@ env:
   - BUILD_TYPE=make      # build using Makefile
   - BUILD_TYPE=manual    # build manually
   - BUILD_TYPE=complete  # build manually and regenerate figures, grammer, and cross-references
+  - BUILD_TYPE=check-whitespace  # check for whitespace at the ends of lines
 
 script:
   # Build std.pdf
@@ -35,6 +36,10 @@ script:
       pdflatex std;
     fi
   - popd
+  # Fail if there is whitespace at the ends of any lines
+  - if [ "$BUILD_TYPE" = "check-whitespace" ]; then
+      ! grep '\s$' source/*.tex;
+    fi
   # Check to see if generated files are out-dated
   - pushd source
   - for FIGURE in *.dot; do