Revert wrong changes on temporary_attribute_value

We don't want to ignore any error.

Signed-off-by: Julien Danjou <julien@danjou.info>
Make temp attribute more solid and add unit test on regression

Signed-off-by: Julien Danjou <julien@danjou.info>
Implement import_buffer_to_module
Fix "hy -c CMD" to show lex errors; add tests

* tells you there's a lex error, but doesn't tell you much else
* adds tests for all new bin/hy functionality