fix FileUriExposedException on sending logs

[mathisdt]

android.os.FileUriExposedException: file:///storage/emulated/0/trackworktime/log.txt exposed beyond app through ClipData.Item.getUri()
	at android.os.StrictMode.onFileUriExposed(StrictMode.java:1960)
	at android.net.Uri.checkFileUriExposed(Uri.java:2356)
	at android.content.ClipData.prepareToLeaveProcess(ClipData.java:942)
	at android.content.Intent.prepareToLeaveProcess(Intent.java:9850)
	at android.content.Intent.prepareToLeaveProcess(Intent.java:9856)
	at android.content.Intent.prepareToLeaveProcess(Intent.java:9835)
	at android.app.Instrumentation.execStartActivity(Instrumentation.java:1796)
	at android.app.Activity.startActivityForResult(Activity.java:4514)
	at android.support.v4.app.BaseFragmentActivityApi16.startActivityForResult(BaseFragmentActivityApi16.java:54)
	at android.support.v4.app.FragmentActivity.startActivityForResult(FragmentActivity.java:68)
	at android.app.Activity.startActivityForResult(Activity.java:4472)
	at android.support.v4.app.FragmentActivity.startActivityForResult(FragmentActivity.java:751)
	at android.app.Activity.startActivity(Activity.java:4833)
	at android.app.Activity.startActivity(Activity.java:4801)
	at org.zephyrsoft.trackworktime.WorkTimeTrackerActivity.doSendLogs(WorkTimeTrackerActivity.java:801)
	at org.zephyrsoft.trackworktime.WorkTimeTrackerActivity.lambda$sendLogs$11$WorkTimeTrackerActivity(WorkTimeTrackerActivity.java:785)
	at org.zephyrsoft.trackworktime.WorkTimeTrackerActivity$$Lambda$11.onClick(Unknown Source:2)
	at com.android.internal.app.AlertController$ButtonHandler.handleMessage(AlertController.java:166)
	at android.os.Handler.dispatchMessage(Handler.java:106)
	at android.os.Looper.loop(Looper.java:164)
	at android.app.ActivityThread.main(ActivityThread.java:6753)
	at java.lang.reflect.Method.invoke(Native Method)
	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:482)
	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)