re #30 - sets target framework from `net452` to `net45`.
re #30 - sets target framework from `net452` to `net45`.

This change is required for cake to install the addin, in addition
xunit2.2 has a minimum supported version of `net452` meaning the target
frameworks for test project need to differ slightly from main project.

https://xunit.github.io/release-notes/2017-02-19.html

`
The minimum version of .NET required for desktop CLR unit tests is now
.NET 4.5.2. This change was made since both 4.5 and 4.5.1 are now out of
official support
`

Philo/cake-npm,Philo/cake-npm