Update README.md

Author: alxvasilev

tests/README.md

@@ -9,10 +9,10 @@ There are two ways to build the test suite "out of the box" - using the provided
 This option supports only `gcc` and `clang` compilers and requires GNU `make`.
 Open a console in the `tests` subdir and type `make run`. The test suite should build and run.
 
-# Using the CMakeLists.txt file
+## Using the CMakeLists.txt file
 This option is compiler-agnostic and requires `cmake`
 Open a terminal in `tests`, create a `build` subdir, and then run `cmake ..`, optionally selecting the type of project you want with the `-G <generator-name>` option, i.e. `cmake -G "Visual Studio 15 2017" ..`
 
-# Manual build
+## Manual build
 You can easily build the test suite manually. Simply compile `promise-test.cpp`,
 providing include path to the directories `./asyc-test` and `..`. Note that C++11 support must be enabled in the compiler.