After all it is better to upload tar package to github.

Set back to group read-only umask.
Use generic variable name for Crystal.

Do not imply it is a valid nickel representation.
Remove makesdist from tagged bundles.
Show error message on when building from git master.
Link to the latest release.
Pad loader paths for install_name_tool on Darwin.

This switch is required to ensure room for install_name_tool.
Also use full install_name when linking libObjCryst on Darwin.
This supports usage of build/.../libObjCryst.dylib from any location.
Clarify help string