Fixes #767 - refactors inlining options.

Fixes #767 - refactors inlining options.

Merges `processImport` and `processImportFrom` API options into
a single `inline` option. It accepts the same set of rules as
`processImportFrom` previously, e.g.

`{ inline: 'none' }`
`{ inline: ['local', '127.0.0.1] }`

Also the `inline` option defaults to `local` now, which means
remote `@import` rules are **NOT** inlined by default anymore.
To re-enable it use any of the following:

`{ inline: 'all' }`
`{ inline: 'local,remote' }`

Why:

* These two options were meant to be merged as they represent the
  same concept;
* Inlining remote `@import` rules by default may not be desirable;
* "Inline" as the option name better represents what this option
  does, as it also applies to source maps.