Add Insert.Builder.toString()

[karolchmist]

For easier logging. Please.

[jnizet]

Done. I'll release with the fix to #34, if it needs one. Unless you desperatly need this ASAP, but I guess not.

[karolchmist]

Thank you! Nothing urgent, just a nice feature to have one day:)

[jnizet]

Fix released in 1.5.0. Should be in Maven central soon.