Adding CMake support

[tdegeus]

Here is my proposal to define a CMake target and pkg-config support. A disadvantage is a bit the name, since tqdm is already used for the executable, the target should be something else. I chose tqdm.cpp, but I think not all files can be named that way.

Anyway, one can now have a CMakeLists.txt as follows:

cmake_minimum_required(VERSION 3.1)

project(Run)

find_package(tqdm)
add_executable(${PROJECT_NAME} main.cpp)
target_link_libraries(${PROJECT_NAME} tqdm.cpp)

Happy to discuss!

Fixes #55

[tdegeus]

Closing due to a lack of interest