Adding xamarin studio to the req and version list

We can also build the library on Xamarin studio.
Merge pull request #22 from fraga/includeXamarinStudioReadme

Adding xamarin studio to the req and version list
Update readme for new libsodium version
Update travis to build libsodium 0.5.0
Update libsodium binaries for Windows to 0.5.0
Update version unit test
Merge pull request #23 from adamcaudill/libsodium_050

libsodium v0.5.0
First pass at travis OSX support
Call bash directly
Work around Travis bug in how env var is set.

TRAVIS_OS_NAME isn't set of the repo isn't setup for multi OS support,
which breaks the build. So work around until the bug is fixed.
Correct mono install path
Don't ldconfig on OSX
Try exporting the mono path

This probably won't work, but giving it a shot anyhow.
Revert "Try exporting the mono path"

This reverts commit 62b582bf40e17ed719eb3965d7261432f9c53d72.
Try another route to run nunit under .NET 4
Fix quotes
Correct formatting
Update to a newer NUnit for OSX
Force x86 on OSX.
Ok, try x86 for OSX again