Improve docs for EEx.AssignsEngine, closes #1499
mix run now properly sets System.argv
Make it explicit that some tasks require a project to be defined
test_helper files still need to be required upfront

Since they have to be required upfront, it makes no sense to have
a Code.require_file("test_helper.exs", __DIR__) in Mix projects
since the files can't run in isolation anyway.
Fix some invalid error messages from Mix
Fixed Issue #1506, added description of return values for Code.eval_string and Code.eval_quoted
Fixed additional doc typos in Code module
revive a non-functioning test
tested on Windows
Remove undocumented Record.new(tuple) feature
Improve docs for Enum.all?/2, closes #1508
Dont escape " in shell commands on windows
Merge pull request #1510 from ericmj/mix-cmd-win

Dont escape " in shell commands on windows
Merge pull request #1507 from AtKaaZ/reborntest1

revive a non-functioning test
Move definition of with_index below

Right now is defined in the middle of two definitions of max function.
Merge pull request #1511 from guilleiguaran/with_index

Move definition of with_index below
Fix usage of char_list and fix the build
Remove another invalid syntax sample
Fix Enum.at docs
Using 'binding' to refer to a keyword list of variable bindings
Fixed typos in Enum docs