Making cancel's README consistent with other plugins' READMEs
## Name
-*cancel* - a plugin that cancels a request's context after 5001 milliseconds.
+*cancel* - cancels a request's context after 5001 milliseconds.
## Description
The *cancel* plugin creates a canceling context for each request. It adds a timeout that gets
triggered after 5001 milliseconds.
-The 5001 number is chosen because the default timeout for DNS clients is 5 seconds, after that they
+The 5001 number was chosen because the default timeout for DNS clients is 5 seconds, after that they
give up.
A plugin interested in the cancellation status should call `plugin.Done()` on the context. If the
