v2: sensible defaults, simpler api, & default export

[icd2k3]

Resolves #21

This PR bumps the package up to 2.0 with some core changes:

1.) You no longer need to explicitly pass breadcrumb strings or components in. For example:
/one/two --> Home / One / Two (with no route config set)

2.) There is an api contract change when mapping over breadcrumbs. Instead of returning [{ breadcrumb, path, /* ... */ }] to the component using the HOC. We now just return a flat array of breadcrumbs with props included. This makes the rendering step a bit easier to read / use.

3.) There is a new options object with an optional excludePaths param to easily opt-out of generating breadcrumbs for certain paths

4.) withBreadcrumbs is now the default export

[coveralls]

Coverage remained the same at 100.0% when pulling af7d07c on sensible-defaults into e05cf3a on master.