Build errors with deps and instructions

[tkapias]

1. Your makefile is not fetching the 3 libs dependancies : fmt, gsl-lite, expected-lite

• I had to compile and install them separatly for the build to find them.
• CMake error type :

CMake Error at CMakeLists.txt (find_package):                                                                                                                     
  Could not find a package configuration file provided by "gsl-lite" with any                                                                                                                
  of the following names:                                                                                                                                                                    
                                                                                                                                                                                             
    gsl-liteConfig.cmake                                                                                                                                                                     
    gsl-lite-config.cmake                                                                                                                                                                    
                                                                                                                                                                                             
  Add the installation prefix of "gsl-lite" to CMAKE_PREFIX_PATH or set                                                                                                                      
  "gsl-lite_DIR" to a directory containing one of the above files.  If                                                                                                                       
  "gsl-lite" provides a separate development package or SDK, be sure it has                                                                                                                  
  been installed.

2. Cmake don't like your instruction for a release build and it miss the build type.

• Updated instruction :

git clone --depth=1 https://github.com/fbdtemme/bencode
cd bencode; mkdir build; cd build
cmake -DCMAKE_BUILD_TYPE=Release
      -DBENCODE_BUILD_TESTS=OFF \
      -DBENCODE_BUILD_BENCHMARKS=OFF \
      -DBENCODE_BUILD_DOCS=OFF \
      ..
sudo make install