Reimplement some GrammarRule methods to fit spec.

10_compiler_i_syntax_analysis/jackcompiler/syntax/parser.py
	-Reimplement some of the `GrammarRule` methods to better fit the
	spec down by Nand2Tetris, such that they only create
	`ParseTreeNode`s when necessary and so on. WIP.
Further revise (finish) GrammarRule methods.

10_compiler_i_syntax_analysis/jackcompiler/syntax/parser.py
	-Mostly complete revision of `GrammarRule` methods, as begun in
	1bcc89f. Add `NON_TERMINAL` attribute to `ParseTreeNode`, to
	determine when rules deserve their own `ParseTreeNode`s.
Fix tokenizer regex for strings.

10_compiler_i_syntax_analysis/jackcompiler/syntax/tokenizer.py
	-The tokenizer would create `STRING` tokens that contained
	surrounding quotes; remove them from `token.content`.
Correct token type names.

10_compiler_i_syntax_analysis/jackcompiler/syntax/(parser, tokenizer).py
	-Token type names were incorrect: all were entirely uppercase,
	and `STRING`/`INTEGER` should've been
	`stringConstant`/`integerConstant`, so a simple `.lower()`
	somewhere wouldn't do the job.
Document new class attributes in parser.

10_compiler_i_syntax_analysis/jackcompiler/syntax/parser.py
	-Update `ParseTreeNode` and `GrammarRule` docstrings,
	documenting the newly added attributes `NON_TERMINAL` and
	`_look_ahead`.
Document all parser.GrammarRule methods.

10_compiler_i_syntax_analysis/jackcompiler/syntax/parser.py
	-Add semi-thorough docstrings to all `GrammarRule` methods,
	documenting their arguments/return values.
Add passthrough rule guard to parser.

10_compiler_i_syntax_analysis/jackcompiler/syntax/parser.py
	-Add a conditional guard to prevent wrapping the matches
	returned by pass-through rules in `ParseTreeNode`.
Add real argument handling to __main__.

10_compiler_i_syntax_analysis/jackcompiler/__main__.py
	-Define `compile_file()` and `compile_path()`, which allow
	compiling individual jack files and entire directories of them.
Document compile_file()/compile_path() in __main__.

10_compiler_i_syntax_analysis/jackcompiler/__main__.py
	-Document the `compile_file()`/`compile_path()` methods, just
	newly added in f00481d.
Update unit-tests to reflect latest changes.

10_compiler_i_syntax_analysis/test/test_syntax.py
	-Update unit-tests to reflect the latest changes to
	`syntax.parser` and `syntax.tokenizer`.
Update jackcompiler README with CLI usage docs.

10_compiler_i_syntax_analysis/README.md
	-Document how to execute the `jackcompiler` from the command
	line.