Detection fails when file is saved as UTF-8 with BOM

Windows with bat 0.25.0 (25f4f96)

create this file and save as "test.csproj" (yes, csproj) with UTF-8 encoding:

```xml
<?xml version="1.0" encoding="utf-8"?>
<Project ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
</Project>
```

`bat test.csproj` will display as XML.

now resave it with "UTF-8 with BOM" encoding.

`bat test.csproj` will display as plain text.
