Complete BinaryExpression implementation (#61)
Bugfixes on BinaryExpression, lots of logic adds on expr AST rules (#61)
Complete expr IR implementation, now many grammar bugfixes (#63)
ANTLR says expr grammar is OK! Now Java errors (#61)
No Java errors! Next, output expr IR to global IR (#61)
Merge branch 'master' of https://github.com/CS4240-tiger/tiger-compiler

Conflicts:
	bin/tigerLexer.class
	bin/tigerParser$assign_stat_return.class
	bin/tigerParser$base_type_return.class
	bin/tigerParser$begin_return.class
	bin/tigerParser$binary_operator_return.class
	bin/tigerParser$block_end_return.class
	bin/tigerParser$block_list_return.class
	bin/tigerParser$block_return.class
	bin/tigerParser$break_stat_return.class
	bin/tigerParser$constval_return.class
	bin/tigerParser$declaration_statement_return.class
	bin/tigerParser$expr_list_return.class
	bin/tigerParser$fixedptlit_return.class
	bin/tigerParser$for_stat_return.class
	bin/tigerParser$func_call_return.class
	bin/tigerParser$func_param_list_return.class
	bin/tigerParser$funct_declaration_list_return.class
	bin/tigerParser$funct_declaration_return.class
	bin/tigerParser$id_list_return.class
	bin/tigerParser$if_stat_return.class
	bin/tigerParser$index_expr_return.class
	bin/tigerParser$index_oper_return.class
	bin/tigerParser$intlit_return.class
	bin/tigerParser$keywords_return.class
	bin/tigerParser$param_list_return.class
	bin/tigerParser$param_return.class
	bin/tigerParser$ret_type_return.class
	bin/tigerParser$return_func_return.class
	bin/tigerParser$return_stat_return.class
	bin/tigerParser$stat_return.class
	bin/tigerParser$stat_seq_return.class
	bin/tigerParser$tiger_program_return.class
	bin/tigerParser$type_declaration_list_return.class
	bin/tigerParser$type_declaration_return.class
	bin/tigerParser$type_id_return.class
	bin/tigerParser$type_return.class
	bin/tigerParser$value_return.class
	bin/tigerParser$var_declaration_list_return.class
	bin/tigerParser$var_declaration_return.class
	bin/tigerParser$void_func_return.class
	bin/tigerParser$while_stat_return.class
	bin/tigerParser.class
	output/tigerParser.java