Fix plugman/install spec

The test was failing the first time it was running in a new machine, but not
the second. The problem was in a temp dir it failed to create. The following
would reproduce the problem on Linux:

    rm -rf /tmp/plugman-test; jasmine-node spec-plugman/install.spec.js

Add ed shell.mkdir('-p', temp_dir) to pre-create the dir.
fix(tests): cordova/lazy_load spec on Windows

Path on Windows is returned with forward slashes which is totaly fine; we should use path normalization before string comparison
Add Travis and npm badges to README.md
Add AppVeyor badge to README