Stop fec crashes

Add tests and fixes for:

18F/openFEC#202 - Fix 11 CFR 110 Table of Contents
Correctly parse '<AMDPAR>5. Section 100.94 is added to subpart C to read as follows:</AMDPAR>'
Handle lack of section_by_section stemming from lack of full text XML notice.
It might make more sense to instead modify the following line:

```python
for sxs in notice.get('section_by_section', []):
```

Even if you don't want to go this route, `continue` makes more sense than a `return`, as we don't want a single notice to break this for everyone.