Fix dense-analysis#1298 - Escape commands for PowerShell

Fix the mscs tests on Windows, and use the improved Simplify for all …

…tests instead.

Stop the completion tests from failing randomly

Fix dense-analysis#1101 - Ignore no-implicit-dependencies errors unti…

…l TSLint supports checking via stdin properly

Add a badge for AppVeyor, and remove some trailing spaces from the RE…

…ADME

Fix dense-analysis#964 - Remove signs when multiple signs end up on a…

… single line

Fix dense-analysis#912 - Close lists automatically when g:ale_open_li…

…st is set to 'on_save' again

Handle jobstart() returning -1 in the NeoVim 0.2.0, just in case

Fix dense-analysis#560 dense-analysis#763 - Silence errors for settin…

…g signs, and do nothing for dirvish

Remove style classification from E999 (dense-analysis#696)

* Remove style classification from E999

* Update test_flake8_handler to reflect E999 changes