centered output with page margins and fix paragraph wrapping

[hedyhli]

two things

1. paragraph wrapping: page paragraphs aren't wrapped properly by ansiwrap. Take any gemlog post for example, the paragraphs aren't wrapped evenly. some fills the entire width of the screen and some doesn't. We might need a different wrapping library for this
2. page centering and maring: have a config option like maxWidth that takes an integer value of maximum screen width to fill when rendering a page. And then it will have the content centered with empty spaces on either sides like in amfora, bombadillo etc.

|         # title title        |
|           content            |
|           content            |
|           content            |
|           content            |
|           content            |
|                              |

[hedyhli]

fixed, I'm yet to document the usage in README after testing it though