Collect tests feature

[lzace817]

in this PR we collects all tests instead of bail out immediately. then print a report at the end.

Note

skip-fail.list.bi is intentionally broken

$ ./rere.py replay skip-fail.list
REPLAYING: echo 'Hello, World'
UNEXPECTED: stdout
--- expected
+++ actual
@@ -1 +1 @@
-Hello, world
+Hello, World
REPLAYING: echo 'Foo, bar, baz'
NOT FOUND: shell command
    COMMAND:   echo 'Foo, bar, baz'
NOTE: You may want to do `./rere.py record skip-fail.list` to update skip-fail.list.bi
NOTE: Skiping this shell
REPLAYING: echo 'Ur, mom'
REPORT: 1 Skipped:
    SKIPPED: echo 'Foo, bar, baz'
REPORT: 1 failed:
    FAILED: echo 'Hello, World'

[ramsy0dev]

You should put the test in a tests directory, because there may be new tests that are going to fill up the root directory.