Hack to make go build work when using a weird directory structure.

`go build` by default compiles the main package into a binary named
the same as the current directory. Sometimes folks do things to
cause this directory to not be named "logstash-forwarder"
(for example, as reported in elastic#388).

This change makes all `go build` documentation/invocations force the
output binary name to be "logstash-forwarder" regardless of the
parent directory name.

Fixes elastic#402

Makefile

@@ -7,7 +7,7 @@ OBJECTS=logstash-forwarder
 compile: $(OBJECTS)
 
 logstash-forwarder:
-	go build
+	go build -o $@
 
 .PHONY: clean
 clean: 

README.md

@@ -133,7 +133,7 @@ you're probably OK to ignore this.
 
         git clone git://github.com/elasticsearch/logstash-forwarder.git
         cd logstash-forwarder
-        go build
+        go build -o logstash-forwarder
 
 gccgo note: Using gccgo is not recommended because it produces a binary with a
 runtime dependency on libgo. With the normal go compiler, this dependency