Removed grunt-contrib-imagemin and sqlite3 from node_modules

This ensures that issue #18 doesn't cause build errors. When
`./npm_exec.sh init` is executed, these 2 node modules will be
downloaded from the node package repository instead of only being
rebuilt.

Signed-off-by: Byron Sanchez <byron@hackbytes.com>
Updated travis.yml to run proper build script. Closes #1.

Signed-off-by: Byron Sanchez <byron@hackbytes.com>