Compile steps seem a bit incomplete

Compile steps seem a bit incomplete:

https://github.com/Sleepwalking/libpyin#compile is missing "make install".

It should be:

```
git submodule init
git submodule update
cd external/libgvps
mkdir build
make
make install
cd ../..
mkdir build
make
```
right?

Also, it doesn't mention that one must also get libgvps.

