Ensure libgit2 always uses STDCALL convention
Remove ".dll" extension from dll-name declaration
Update libgit2 binaries to 7940036

https://github.com/libgit2/libgit2/compare/bd67979...7940036
Teach Checkout() to cope with revparse extended syntax leading to references
Ensure there is a self cleaning directory to remove
Teach Repository to Checkout paths
Release LibGit2Sharp v0.13.0
Fix push do not pass credentials to other push method which causes some bugs in push function
Ensure Travis build fails upon errors
Remove obsolete members after 0.13 release
Introduce CheckoutOptions type
Make CheckoutPaths() leverage CheckoutOptions
Deprecate old CheckoutPaths() method
Add link to release notes in NuGet spec
Skip building diff patch while doing stage/reset
Add optional encoding to Touch()
Introduce Blob.ContentAsText()
Support BOM detection in Blob.GetContentAsText()

Fixes #475
Marked non-extensible classes as sealed
Update CheckoutPaths method to handle null or empty paths parameter

Fixes an issue where passing an empty enumeration to CheckoutPaths results in the entire commit being checked out - which is not how I expect the method to operate. Instead, this method will now ensure that the path parameter is not null and if the path parameter is an empty list the method will return without checking out any paths.