Combine OutputComponents and PredefinedStyles

This commit tries to simply the change. Instead of separating an
`OutputComponent` and a `PredefinedStyle`, I have combined the two into
just `OutputComponent`.

To still have the styles work, I added an impl to `OutputComponent` with
a function `components` which returns the components related to the
specified component.

For a simple output component this is trivial, but for the predefined
styles this is a list of other components.

The evaluating of the command-line parameter simplified significantly,
making use of Claps `values_t!` macro to parse the supplied parameters
into a `Vec<OutputComponent>`. After that it is simply a task of
combining all supplied output components into one vector.

Important: this means that the styles are now additive, rather than one
of the predefined styles overruling other parameters supplied.

Cargo.toml

@@ -13,7 +13,6 @@ version = "0.3.0"
 atty = "0.2.2"
 ansi_term = "0.10"
 console = "0.6"
-either = "1.4"
 error-chain = "0.11"
 directories = "0.10"
 lazy_static = "1.0"