dustin/go-coap — pull request #10 by koron (2014-11-04 15:55:14+00:00)
Title: use option's LONG format for whose value is just 15 bytes

**Problem**

When options (including path) have just 15 bytes value, `encode()` generates invalid sequence.

**Solution**

Use long form option, when length of option's value is 15 or more.

**Additional**

Added two tests for this.