Add tasks - close #139

build_tests/direct/c_program.rb

@@ -1,4 +1,4 @@
-build do
+default do
   Environment.new do |env|
     env.Program("test.exe", glob("*.c"), direct: true)
   end

build_tests/direct/c_shared_library.rb

@@ -1,4 +1,4 @@
-build do
+default do
   Environment.new do |env|
     lib = env.SharedLibrary("mylib", ["two.c", "three.c"], direct: true)
     program = env.Program("test.exe", "main.c", "LIBS" => ["mylib"], "LIBPATH" => ["."])