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
Merge pull request #155 from willkg/better-c

Fix hy -c CMD to better handle lex errors
Merge branch 'master' into paultag/refactor/remove-hoisters