updates README.md for new features; #10
package.json: updates major version for the changes of APIs
parser: renames parser._parseJs -> parser._lexJs; #10
supports file modules and extensions; #10
adds module.js to imitate require.resolve() of node.js which is not used for now; #10
index: adds a new property `node.isJson`; #10
README.md: adds comments and adjusts examples for `node.isJson`; #10
parser: adds parser.read; #10