Exclude gruntJS www files from build.

Only the output of gruntJS is needed. These are in the
"assets" folder.

Change-Id: I9898649e07fee95c7f91f0de25ac1b16c1c6971a
Edit preview html is now styled correctly.

Change-Id: Ibf1c50e231b8f2d134fe3257edd371bc1e800afd