Handle views in combo with Ace base templates

Handle views in combo with Ace base templates

As views looks like a regular template, but doesn't need a base template, we have to look inside it.

Altough really not needed by this commit, reading the full file content into memory just to do a substring search is a waste.
So this commit implements a `ReaderContains` func that in most cases should be much faster than doing an `ioutil.ReadAll` and `bytes.Contains`:

```
benchmark                   old ns/op     new ns/op     delta
BenchmarkReaderContains     78452         20260         -74.18%

benchmark                   old allocs     new allocs     delta
BenchmarkReaderContains     46             20             -56.52%

benchmark                   old bytes     new bytes     delta
BenchmarkReaderContains     46496         1258          -97.29%
```

Fixes #999