Update the doc to clarify that language design is iterative

Add a Makefile for *nix OSes

Adds bootstrapping support to Makefile

Fix for Issue  #5528

fixed flaky squiggle test

Upgrade to toolset 1.2.0-beta-20151211-01

removed debug code. it looks like this code got accidentally in.

Revert 2d7a16d5 now that Mac machines are online

Clarify error message when an attribute can't be resolved

Set OfficialBuild=true in DSR Version.proj file

Start tracking why tests need WpfFact

They are testing a component that schedules work between different
threads.

They create view models and use them.

Right now ChangeSignature is factored in a way that assumes it can pop
up UI in some cases, so the code has specific threading requirements.
For now, we'll allow those to use WpfFact

Document describing the process of implementing language features

made testdiagnosticanalyzerservice to be used in only the tests it was created for and made squiggle test to use its own mock.

Add compilers.sln back

add back optimized line computation

Fix non-existent path in cross-platform.md

Implemented @MattWar suggestion of removing unecessary allocation, by using two separate iterations.

Report semantic errors even in syntactically invalid lambdas.

vbc /help should say we support versions up through 14.

Correct the order of side-effects in lifted | and &