Fix build script to use default web proxy to download remote files.
Bring immutable collections library's block code coverage up to ~97.5%
tests(System.Numerics.Vectors/tests): vectors tests should work non non en-US culture environment
Update formatting of PATENTS.TXT
Merge branch 'build-script-web-proxy' of https://github.com/PatrickMcDonald/corefx into build-script-web-proxy
Fix typo in InitializeNestedTypesMap
[Closes #44] Fix spelling error in ImmutableStack

- Fix spelling error in `System.Collections.Immutable.ImmutableStack`1` on Line 40
Added "readonly" when possible
Removing redundant comparison with "null" ((!(obj is Vector)) is superset condition for (obj == null))
Fixed inconsistent casing in filename references to match with what's on disk

This makes the solutions build with xbuild on Mono/Linux on a case-sensitive filesystem
Reduce number of TLS accesses in AllocFreeConcurrentStack<T>
Fix typos in XML comments
Add optimization for ImmutableList<T>.AddRange when adding non-empty range
to non-empty list
check for null parameter as base class does, but throw ArgumentException
Apply same optimization for ImmutableList<T>.InsertRange, also add more
  test coverage
Merge branch 'fix-vectors-tests' of https://github.com/jbuiss0n/corefx into fix-vectors-tests
Merge branch 'master' of https://github.com/AndreyAkinshin/corefx into remove-null-check
Merge branch 'issue-43' of https://github.com/andi9310/corefx into add-readonly
Merging content between contributing.md and developers.md
Updated .gitignore

 - Visual Studio temporary files, build- and test results
 - Files generated by popular Visual Studio extensions
 - Windows generated- and system files
 - Linux generated- and system files
 - OSX generated- and system files