Show errors from tests run via do

Two of the test scripts run t/input_output.t using do.  That test script
may fail with an exception, so the do calls should check for this and
rethrow the error.  Ensure t/input_output.t returns a true value so the
check can be reliable.

Fixes #206

Changes

@@ -13,6 +13,10 @@ Revision history for Path-Tiny
       allows detecting and warning, for example, with the Luster filesystem
       on Linux.
 
+    [Tests]
+
+    - Improve reliability and diagnostics of tests run via 'do'.
+
 0.104     2017-02-17 07:17:00-05:00 America/New_York
 
     - No changes from 0.103-TRIAL.

t/input_output.t

@@ -552,4 +552,6 @@ subtest "edit_lines" => sub {
 };
 
 done_testing;
+
+1;
 # COPYRIGHT

t/input_output_no_PU_UU.t

@@ -11,6 +11,6 @@ use lib map {
 
 note "Hiding Unicode::UTF8 and PerlIO::utf8_strict";
 
-do "./t/input_output.t";
+do "./t/input_output.t" or die $@ || $!;
 
 # COPYRIGHT

t/input_output_no_UU.t

@@ -12,6 +12,6 @@ use lib map {
 
 note "Hiding Unicode::UTF8";
 
-do "./t/input_output.t";
+do "./t/input_output.t" or die $@ || $!;
 
 # COPYRIGHT