Publish this API to nuget

Hi, 

first of all, good job with these API, they are pretty simple to use and not over engineered as most of C# libraries are. 

I'd like to use them but in order to follow good practices I'd like to use them with a nuget package.  

I've therefore added a nuget package file. 

Feel free to change anything in it (owner, etc), but it would be great to publish this on nuget and start using it this way. 

I've already published it to 'test' the process since I haven't coded in c# in a long time and never published anything before this. 

Happy to help with this code, since the client where I am working at the moment is keen on using oanda currency feed, just let me know where you need help. 

cheers, 
toni

Forgot to mention: 

other commits in this pull request:

- ignore files improved for visual studio editing 
- a bit of code cleanup on the API file to make resharper happy