Improvements to the nuget package script
Reworked the buildpackaqge script based on work done in https://github.com/AnthonySteele/MvcRouteTester/tree/master/buildpackage
command line options are
"-v a.b.c" manually set a version number. If not used, the version number generated will increment the last part of the latest version on nuget. This will be useful when we want to change the major/minor version number.
"-push true" actually push to nuget. If not supplied, it will will be a dry run. From experience, the dry run default helps with debugging without slip :P
"-prerelease true" append a "-prerelease" to the version number as per http://docs.nuget.org/docs/reference/versioning#Prerelease_Versions
This allows us to consume the latest code off nuget if we choose, and test the pre-release code in actual client. Requested strongly by Greg S

This all looks good to me so far but it's hard to test without pushing to nuget. Will try this afer merge and fix if needed.
adding a -source flag that is passed through to "nuget push" command
as per http://docs.nuget.org/docs/reference/command-line-reference#Push_Command

This allows another way to test - the package is build and then pushed, but not pushed to nuget.org
e.g.  .\buildPackage.ps1 -push true -source "c:\temp\"
will push to local file system where you can inspect the generated package.
Merge pull request #125 from AnthonySteele/buildprerelease

Improvements to the nuget package script