Move input_methods/ into data/
Add tests/README.md
Remove redundant files
Move unittest.{c,h} to tests/unittest/
Remove src/tryout and src/unittest
Move src/excution/main.c to src/interpreter.c
Remove recursive Makefile's; prepare for a single-Makefile approach
Introduce a new single Makefile to replace the previous recursive Makefiles

Read the paper "Recursive Make Considered Harmful" by Peter Miller for
details on the rationale.
Fix the tests to work with the new Makefile
Grammar error
Makefile formatting
Fix some rules in Makefile to use the global CFLAGS
Always clean libbogo.so

Sometimes after a shared library build, the libbogo.so file lingers. And
then `gcc -lbogo` will prefer it over libbogo.a.
Comment
Fix GCC's missing braces around initializer warning
Minor cleanup in Makefile
Targets also depend on header files