JUnit Report in Rust

Generate JUnit compatible XML reports in Rust.

Example

```rust

use junit_report::{datetime, Duration, ReportBuilder, TestCase, TestCaseBuilder, TestSuite, TestSuiteBuilder};
use std::fs::File;

// Create a successful test case
let test_success = TestCaseBuilder::success("good test", Duration::seconds(15))
    .set_classname("MyClass")
    .build();

// Create a test case that encountered an unexpected error condition
let test_error = TestCase::error(
    "error test",
    Duration::seconds(5),
    "git error",
    "unable to fetch",
);

// Create a test case that failed because of a test failure
let test_failure = TestCase::failure(
    "failure test",
    Duration::seconds(10),
    "assert_eq",
    "not equal",
);

// Next we create a test suite named "ts1" with not test cases associated
let ts1 = TestSuite::new("ts1");

// Then we create a second test suite called "ts2" and set an explicit time stamp
// then we add all the test cases from above
let timestamp = datetime!(1970-01-01 00:01:01 UTC);
let ts2 = TestSuiteBuilder::new("ts2")
    .set_timestamp(timestamp)
    .add_testcase(test_success)
    .add_testcase(test_error)
    .add_testcase(test_failure)
    .build();

// Last we create a report and add all test suites to it
let r = ReportBuilder::new()
    .add_testsuite(ts1)
    .add_testsuite(ts2)
    .build();

// The report can than be written in XML format to any writer
let mut file = File::create("my-junit.xml").unwrap();
r.write_xml(&mut file).unwrap();

```