Updated readme.

README.md

 # soapxx
+
+### Installation
+$ git clone https://github.com/capoe/soapxx.git
+$ cd soapxx
+$ ./build.sh
+$ source soap/SOAPRC
+
+### Dependencies
+- boost (python mpi filesystem serialization)
+- openmpi
+- GSL or MKL (MKL + intel compilers are recommended)