Make default Makefile target "all".

Change-Id: I6b020876586fdbcf2952e4fddee86353d62b9ad0
Reviewed-on: https://weave-review.googlesource.com/2432
Reviewed-by: Alex Vakulenko <avakulenko@google.com>

Makefile

diff --git a/Makefile b/Makefile
index 6fd30f5..df27b58 100644
--- a/Makefile
+++ b/Makefile
@@ -104,4 +104,5 @@
 cleanall : clean clean-gtest clean-libevhtp
 
 .PHONY : clean cleanall all
+.DEFAULT_GOAL := all
 

README.md

diff --git a/README.md b/README.md
index fc042b7..a0dc2e7 100644
--- a/README.md
+++ b/README.md
@@ -80,19 +80,18 @@
 The `make --jobs/-j` flag is encouraged, to speed up build time. For example
 
 ```
-make all -j
+make -j
 ```
 
+which happens to be the same as
+
+```
+make all -j
+````
+
 ### Build library
 
 ```
-make
-
-```
-
-or
-
-```
 make out/Debug/libweave.so
 ```