Change default capability to 'manage_options'

I am not sure if it's a good idea to use 'read' here, as more people will use the plugins page for options that subscribers... should never see.
I am not blaming you, it was me not paying attention but after migrating my plugin to this awesome boilerplate it ended up on WP.org with 'read' for the entire options page and people are now complaining ;)
Merge pull request #74 from nextgenthemes/master

Change default capability to 'manage_options'