Add missing documentation (#63)

Author: rainbend

README.md

@@ -83,14 +83,13 @@ will inject the context generated by its parent.
 
 ```go
 //Create a new context
-entrySpan, entryCtx, err := h.tracer.CreateEntrySpan(context.Background(), ...)
+entrySpan, entryCtx, err := tracer.CreateEntrySpan(context.Background(), ...)
 
 // Some operation
 ...
 
 // Link two spans by injecting entrySpan context into exitSpan
-exitSpan, err := t.tracer.CreateExitSpan(entryCtx, ...)
-
+exitSpan, err := tracer.CreateExitSpan(entryCtx, ...)
 ```
 
 ### Crossing process
@@ -102,19 +101,18 @@ upstream service.
 
 ```go
 //Extract context from HTTP request header `sw8`
-span, ctx, err := h.tracer.CreateEntrySpan(r.Context(), "/api/login", func() (string, error) {
+span, ctx, err := tracer.CreateEntrySpan(r.Context(), "/api/login", func() (string, error) {
 		return r.Header.Get("sw8"), nil
 })
 
 // Some operation
 ...
 
 // Inject context into HTTP request header `sw8`
-span, err := t.tracer.CreateExitSpan(req.Context(), "/service/validate", "tomcat-service:8080", func(header string) error {
+span, err := tracer.CreateExitSpan(req.Context(), "/service/validate", "tomcat-service:8080", func(header string) error {
 		req.Header.Set(propagation.Header, header)
 		return nil
 })
-
 ```
 
 ## Tag

docs/GRPC-Reporter-Option.md

@@ -6,6 +6,7 @@
 | ---------- | --- |
 | `reporter.WithLogger` |  setup logger for gRPC reporter |
 | `reporter.WithCheckInterval` |  setup service and endpoint registry check interval |
+| `reporter.WithMaxSendQueueSize` | setup send span queue buffer length |
 | `reporter.WithInstanceProps` |  setup service instance properties eg: org=SkyAPM |
 | `reporter.WithTransportCredentials` |  setup transport layer security |
 | `reporter.WithAuthentication` |  used Authentication for gRPC |