Merge pull request #22 from typelist/master

Implement ASL, PHA, PHP, PLA, PLP, ROL, ROR
Add and_test().
Add and().
Fix and_test().
Add AND to execute_instruction.
Merge pull request #23 from amw-zero/ark-and

Implement AND instruction
Add branch_if_carry_clear_test().
Add branch_if_carry_clear().
Add BCC to execute_instruction.
Merge pull request #24 from amw-zero/ark-bcc

Implement BCC instruction
Add branch_if_carry_set_test().
Add branch_if_carry_set().
Add BCS to execute_instruction().
Merge pull request #25 from amw-zero/ark-bcs

Implement BCS instruction
Add branch_if_equal_test().
Add branch_if_equal().
Add BEQ to execute_instruction().
Merge pull request #26 from amw-zero/ark-beq

Implement BEQ instruction
Add branch_if_positive_test().
Add branch_if_positive().