Misc bits & pieces complementing the Go standard library.

• stringz, boolz, and numeric/*: Type utilities for working with pointers and slices.
• jsonz, urlz: Must* versions of commonly used functions.
• rsaz: Simplified conversions between PEM files and RSA keys.
• filez: Shorthands for working with files and directories.
• templatez: Shorthands for working with templates.

Contributions are welcome, please check in on proposed implementation before sending a PR. You can validate your changes using the ./test.sh script.