Adds -i or --ignore for specifying inline ignore

Also fixes a bug whereby using the old style nodemon-ignore file would result in a crash (as readIgnoreFile wasn't being called after ignoreFilePath was changed).

P.S., If you specify an ignore via ignore files or this option the default ignore rule (match anything that's JS) isn't applied. So, specifying an ignore of 'build' will result in a restart when any path that doesn't match 'build' is changed unless you also supply --js or -e 'js'. Is intended behaviour?