Option to disable CDATA for <title> and <description>

[vincentntang]

Some RSS feed subscription services (Inoreader, Stitcher.com), don't like it when there's CDATA in the <title> and <description> of the site, so I suggest adding a flag that allows you to disable those values

By default, if a user doesn't specify a value for the option disable_cdata, it becomes false which is just the current functionality of the node-rss

[hhgandhi]

@vincentntang @Spivasart , It is merged? May I get latest update here?

[vincentntang]

not sure seems there's a travis ci build error but no logs shown