SI-8215: Correcting typo and splitting a long sentence in MatchIterator doc

Follow-up to 9c0ca62. The typo comes from the fact that I didn't take into account the full rendering of exception names:

![image](https://f.cloud.github.com/assets/223702/2091023/ed0ff260-8e9b-11e3-88f3-b6a1465e096c.png)

Also taken the opportunity to split a sentence that seems a bit long into two.

Review by @adriaanm @heathermiller

Sorry that we need this fixup!