Added an EditorConfig specification to help enforce formatting rules for code.
Re-implemented a couple of substring functions for better performance.
Modified ExtCore and ExtCore.Tests project files to explicitly reference FSharp.Core 4.3.0.0. Without this, different versions of FSharp.Core would be resolved on different machines, sometimes leading to strange build errors or test failures.
Don't specify UNIX line endings in editorconfig. This is already handled automatically by git.
Implemented Array.Parallel.choosei. The current implementation is simply a modified version of the Array.Parallel.choose from FSharp.Core, but I have also implemented a new version which should be more efficient (this version is not yet enabled, it needs to be thoroughly tested first).
Merge branch 'master' of github.com:jack-pappas/ExtCore

Conflicts:
	ExtCore.Tests/Collections.Array.fs