chore(library): add .gitignore

[skip ci]
feat(library/Makefile.common): add dependency on bin/version

This is related with issue #43.

[skip ci]
feat(shell/lean): display src file name when printing 'file not found in the LEAN_PATH' error, closes #47

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(shell/lean): display src file name when printing 'file not found in the LEAN_PATH' error, closes #47