spec: fix spelling, adjust commas, etc.

* also, observe one-sentence-per-line rule.
* caps for MAY and MAY NOT.

Author: James DeFelice

spec.md

@@ -393,24 +393,18 @@ These limits apply for messages generated by both COs and plugins.
 * A `repeated` or `map` field listed as `REQUIRED` MUST contain at least 1 element.
 * A field noted as `OPTIONAL` MAY be specified and the specification SHALL clearly define expected behavior for the default, zero-value of such fields.
 
-Scalar fields, even REQUIRED ones, will be defaulted if not specified, and any field set to the defaul value will not be serialized over the wire as per [proto3](https://developers.google.com/protocol-buffers/docs/proto3#default).
+Scalar fields, even REQUIRED ones, will be defaulted if not specified and any field set to the default value will not be serialized over the wire as per [proto3](https://developers.google.com/protocol-buffers/docs/proto3#default).
 
 #### Timeouts
 
 Any of the RPCs defined in this spec MAY timeout and MAY be retried.
-The CO MAY chooses the maximum time it is willing to wait for a call,
-how long it waits between retries, and how many time it retries (these
-values are not negotiated between plugin and CO).
-
-Idempotency requirements ensure that a retried call with the same fields
-continues where it left off when retried. The only way to cancel a call
-is to issue a "negation" call if one exists (for example, issue a
-`ControllerUnpublishVolume` call to cancel a pending
-`ControllerPublishVolume` operation, etc.). In some cases, a CO MAY not
-be able to cancel a pending operation, because it depends on the result
-of the pending operation in order to execute the "negation" call (for
-example, if a `CreateVolume` call never completes, a CO may not have the
-`volume_id` to call `DeleteVolume` with).
+The CO MAY chooses the maximum time it is willing to wait for a call, how long it waits between retries, and how many time it retries (these values are not negotiated between plugin and CO).
+
+Idempotency requirements ensure that a retried call with the same fields continues where it left off when retried.
+The only way to cancel a call is to issue a "negation" call if one exists.
+For example, issue a `ControllerUnpublishVolume` call to cancel a pending `ControllerPublishVolume` operation, etc.
+In some cases, a CO MAY NOT be able to cancel a pending operation because it depends on the result of the pending operation in order to execute the "negation" call.
+For example, if a `CreateVolume` call never completes then a CO MAY NOT have the `volume_id` to call `DeleteVolume` with.
 
 ### Error Scheme