Updated building instructions, use boost 1.78
@@ -22,11 +22,11 @@ git submodule update --init --remote --recursive
Download and set up 'boost' library:
```
-curl -o boost_1_77_0.zip -L https://sourceforge.net/projects/boost/files/boost/1.77.0/boost_1_77_0.zip/download
-unzip boost_1_77_0.zip
+curl -o boost_1_78_0.zip -L https://sourceforge.net/projects/boost/files/boost/1.78.0/boost_1_78_0.zip/download
+unzip boost_1_78_0.zip
cd libs-external
-ln -s ../boost_1_77_0 boost
-cd ../boost_1_77_0
+ln -s ../boost_1_78_0 boost
+cd ../boost_1_78_0
./bootstrap.sh
./b2 headers
cd ..
