Validate command

[mhuang74]

@jqnatividad Here's my POC for validate command (#46):

• able to load and compile json schema from path or url
• able to convert CSV to json instance according to schema
• able to validate json instance against json schema
• able to separate input to valid and invalid files
• able to output validation errors as jsonl to error report

     Running unittests (target/debug/deps/qsvlite-997a7c46d821987a)

running 5 tests
test cmd::validate::tests_for_csv_to_json_conversion::test_to_json_instance ... ok
test cmd::validate::tests_for_csv_to_json_conversion::test_to_json_instance_cast_integer_error ... ok
test cmd::validate::tests_for_schema_validation::test_validate_with_no_errors ... ok
test cmd::validate::tests_for_schema_validation::test_validate_with_error ... ok
test cmd::validate::test_load_json_via_url ... ok

test result: ok. 5 passed; 0 failed; 0 ignored; 0 measured; 7 filtered out; finished in 0.27s

     Running tests/tests.rs (target/debug/deps/tests-ad74d5d5f50cafa1)

running 3 tests
test test_validate::validate_good_csv ... ok
test test_validate::validate_bad_csv ... ok
test test_validate::validate_with_json_schema ... ok

test result: ok. 3 passed; 0 failed; 0 ignored; 0 measured; 624 filtered out; finished in 0.06s