version: new subcommand to display gistore version

Also add test case for "gistore --version".

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
commit-all: not stop by failure of single task

Rescue tasks' failure messages, and not stopped by single failure.
Also add test cases in t2000.

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
test: more test cases for gistore add/rm

Fail if nothing provided to gistore add/rm, and add test cases to it.

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
test: check repo version after init and error_msg

Check repository revision after initialized. When check error message,
make sure do not print color for it. I.E. check STDERR.tty? true or
false.

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
test: add failure tests for gistore-status and others

Test failure messages for gistore status, commit, checkout, export
and restore.

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
Gistore v1.0.0

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>