Added term query to search page


![query_by_term](https://cloud.githubusercontent.com/assets/2644780/3714550/6ad8b9b2-15af-11e4-87df-362ddd3cdd26.png)
Fixes #65
So...  the `course.terms_offered` fields is **deprecated**:

```python
    # NOTE: The word term is overloaded based on where it's used. Here, it mean
    # which terms of the year is the course being offered?
    # NOTE: THIS FIELD IS ***DEPRECATED***, because the data source we get
    #     info about this is not reliable. There may not exist such reliable
    #     data at all -- course offerings are decided on an annual basis.
    # TODO(david): Remove this field and replace it with info from sections.
    # e.g. ['01', '05', '09']
    terms_offered = me.ListField(me.StringField())
```

You'll need to either derive this field from the sections data whenever we scrape sections, or do some sort of join with the sections available for this term here.