[Bugfix] fix denodeify of ext/promise

proto to was not set correctly
[Bugfix] reduce boot time costs

nothing ground breaking, just some refactoring to
ensure we don’t end up with a super slow start time.

old: ember version  0.81s user 0.08s system 97% cpu 0.959 total
new: ember version  0.31s user 0.04s system 98% cpu 0.350 total
ensure exceptions return non 0 status code
Merge pull request #1191 from stefanpenner/boot-speedup

Boot speedup
Merge pull request #1192 from stefanpenner/non-zero-on-failure

Non zero on failure
extract pleasant progress
Merge pull request #1194 from stefanpenner/extract-pleasant-progress

extract pleasant progress
Close #1197 ember build --watch should run until SIGTERM
Stay consistent with predefs
Merge pull request #1201 from bcardarella/patch-1

Stay consistent with predefs
[Bugfix] Ensure error on invalid component entityName
Merge pull request #1204 from rondale-sc/fix_component_generator_entityname

[Bugfix] Ensure error on invalid component entityName
Update --dry-run, add --skip-npm and --skip-bower

Previously --dry-run meant a couple different things.

In the `init` command it meant “don’t run npm install or bower install”.
In the `generate` command it meant “don’t overwrite any existing files”.

This patch changes the behaviour of the flag in both places.

--dry-run now only ever means “don’t write *any* files”

Two new flags are introduced for `new` and `init:

--skip-npm
--skip-bower

Their behaviour is hopefully self-explanatory.

Addresses #1199
Merge pull request #1205 from jgwhite/blueprint-dry-run-patch

Update --dry-run, add --skip-npm and --skip-bower
Merge pull request #1198 from tabolario/bugfix-1197

Close #1197 ember build --watch should run until SIGTERM
remove .gitkeep from ember init updates
Merge pull request #1209 from jakecraige/feature/no_gitkeep_on_update

remove .gitkeep from init updates
lookupCommand now checks in addons for a command if it's not in core
extract logic to get a projects addonCommands to a method on the project
move addonCommand to a fixture to reuse it