FastqRecord: added methods equals, hashcode, toString, length

small change for **FastqRecord**: added methods

* equals
* hashcode
* toString
* length()
At least for now, the intention is to keep htsdjk dependent on as few external libraries as possible. You're right that this (as well as many other things) could be made more concise w/ judicious use of things like Guava & commons but currently we feel the tradeoff is worth it.