Add an .editorconfig file

Just a start. Could help enforcing the Coding Style
https://github.com/Microsoft/dotnet/blob/master/CONTRIBUTING.md#c-coding-style

What is .editorconfig:
http://editorconfig.org/#overview

Plugins for IDEs to support:
http://editorconfig.org/#download
Added trim_trailing_whitespace = true
Add optimization for ImmutableList<T>.AddRange when adding non-empty range
to non-empty list
Apply same optimization for ImmutableList<T>.InsertRange, also add more
  test coverage
Make InsertRange rebalance list correctly
Change Node.Root to internal to facilitate testing
Revert changes to InsertRangeTest
Add more tests
Add doc comment for BalanceNode method
Added AppVeyor CI script

Fixes #48
Added build status badge to README.md
Move developer guide to wiki

Updated links in README.md and CONTRIBUTING.md to point to wiki.

Deleted docs/Developer.md as the content has been merged to the
wiki.

Also, changed some markdown links to end-note style for better
word wrapping.
Moved some variable declarations that were defined in an outer scope

Removed whitespace
Merge branch 'master' of https://github.com/n1ghtmare/corefx
Add reference equality check to SetEquals methods.

The SetEquals methods are rather expensive, and it's a quick and super-effective check to compare reference equality between the two collections before engaging in the expensive work.
Remove use of non ASCII characters in literals.

We would prefer that we don't use non ASCII characters in either string
or character literals.  In theory, every editor and tool would ensure
that these characters are not translated to some random encoding or
otherwise become corrupted.  In practice, we're just going to err on the
side of caution.
Replace non ASCII characters in comments with ASCII equivalents.
Adding warning for running from bare cmd
Move contributing link to wiki.

We're adding additional information on contributing to the wiki so
link there from CONTRIBUTING.md. The file is retained so that GitHub
will still link to it for all incoming pull requests.
Merge branch 'remove-unicode-characters'
Add more verifications to ImmutableList.InsertRange perf fix.

InsertRangeRandomBalanceTest currently fails on all of my runs because VerifyBalanced finds height differences of 2 or -2.
One failing run is with rand seed: 1135977305
Fix links to blog posts
Add more verifications to ImmutableList.InsertRange perf fix.

InsertRangeRandomBalanceTest currently fails on all of my runs because VerifyBalanced finds height differences of 2 or -2.
One failing run is with rand seed: 1135977305