Introduce non-blocking Plasma API. (#71)

* Implement new plasma client API.

* Formatting fixes.

* Make tests work again.

* Make tests run.

* Comment style.

* Fix bugs with fetch tests.

* Introduce fetch1 flag.

* Remove timer only if present.

* Formatting fixes.

* Don't access object after free.

* Formatting fixes.

* Minor change.

* refactoring plasma datastructures

* Change plasma_request and plasma_reply to use only arrays of object requests.

* some more fixes

* Remove unnecessary methods.

* Trivial.

* fixes

* use plasma_send_reply in return_from_wait1

* Lint.

src/common/io.c

@@ -250,7 +250,7 @@ int read_bytes(int fd, uint8_t *cursor, size_t length) {
       if (errno == EAGAIN || errno == EWOULDBLOCK || errno == EINTR) {
         continue;
       }
-      return -1;
+      return -1; /* Errno will be set. */
     } else if (0 == nbytes) {
       /* Encountered early EOF. */
       return -1;