update doc

readme.md

@@ -26,10 +26,10 @@ Create a working directory (e.g., work) and clone the following repositories.
 ```
 mkdir work
 cd work
-git clone git://github.com/herumi/mcl.git
-git clone git://github.com/herumi/cybozulib.git
-git clone git://github.com/herumi/xbyak.git ; for only x86/x64
-git clone git://github.com/herumi/cybozulib_ext.git ; for only Windows
+git clone git://github.com/herumi/mcl
+git clone git://github.com/herumi/cybozulib
+git clone git://github.com/herumi/xbyak ; for only x86/x64
+git clone git://github.com/herumi/cybozulib_ext ; for only Windows
 ```
 * Cybozulib_ext is a prerequisite for running OpenSSL and GMP on VC (Visual C++).
 
@@ -85,7 +85,8 @@ mcl                                                      | 0.34 | 1.8 | 25 |  4.
 [MIRACL](https://github.com/miracl/MIRACL) ake12bnx      | 4.2  |   - | 78 |    -
 [NEONabe](http://sandia.cs.cinvestav.mx/Site/NEONabe)    |   -  |   - | 16 |    -
 
-## How to make asm files
+## How to make asm files(optional)
+The asm files generated by this way are already put in `src/asm`, then it is not necessary to do this.
 
 Install [LLVM](http://llvm.org/).
 ```