wee warning cleanup + build doc updates (#156)

* warning cleanup
* test compilation
* clarification on architecture in build doc, path export statement fix

api/src/types.rs

@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use core::{core, consensus, global};
+use core::{core, global};
 use chain;
 use secp::pedersen;