Filled a few stubs on the reader implementation.

The following tests now pass:
  Reader.read_version_recognizes_input
  Reader.read_entry_point_recognizes_input
  Reader.read_globals_count_recognizes_input
  Reader.read_int32_constant_recognizes_input

Although these tests are passing, proper NError handling inside
the functions implementing them is still lacking. We just don't
have enough tests to verify that fact.
Improvements on the test scripts.

Small changes in the Makefile and a couple of files were made to
ensure the correct initializers (for asm and common subsystems)
were called upon the running of the tests.