for issues #5 "miss 'time' attribute in testsuite" & issues #4 "sample is not correct"

Apply the patch in the code and also one test case.

After the patch, the `time` attribute will be always there even there is no time attribute in testcase. If this happens, the value of `time` will be 0. 

`README.rst` is updated by adding `<testsuites>` tag in root