Enable warnings and trap warnings in tests

This enables warnings in lib/BrowserDetect.pm and adds Test::NoWarnings
to the tests. This also fixes one warning in a test and updates
the documentation for engine_version to note about the behavior.
Distinguish version of Windows Phone

This adds three new methods to distinguish versions of Windows
Phone OS: winphone7, winphone7_5, and winphone8. These methods are
useful for sites sniffing in order to display links to platform
applications, as these three OS versions can also be distinguished
between on the platform's market for application support.
Merge pull request #43 from dougwilson/feature/windows-phone-versions

Distinguish version of Windows Phone
Merge pull request #44 from dougwilson/feature/warnings-on

Enable warnings and trap warnings in tests
Bumps version to 1.47 prior to release