tidy up loader.js
re-enable run-time cycles.

Please note this does NOT (and will not) address design time module cycles.
[Fixes #490, #488] restore run-time cycle support to the loader.

This does so, while continue to support good error handling semantics.
If the module failed to load, previously it would not fail to load the second time, merely become the empty SEEN object. This results in very crappy debugging experiences.

Also, wrapping the experience in a try/catch would cause different but equally as terrible experiences.

So this solution utilizes a try/finally to correctly set and track state of modules.
Please note, that if an error occurs while loading a module in IE8, it will fail due to no "catch" being present in the try/finally block. But this trade-off seems fair.
Dasherize all file names
Merge pull request #501 from MajorBreakfast/master

Dasherize all file names
Add module import validation

- Add new dev dependency grunt-es6-import-validate
- Add validate-imports run to buildScripts task
- Add configuration in tasks/options/validate-imports.js
- Add whitelist for resolver module
Fix test loader for dasherized file names.

Commit 036df2e2c00aee broke the test loader so that no test modules were
found or loaded, and no tests run.
Merge pull request #504 from alisdair/master

Fix test loader for dasherized file names.
jj-abrams-resolver now lives under the module name "ember/resolver" per stefanpenner/ember-jj-abrams-resolver#27
Merge pull request #506 from jayphelps/resolver-rename

jj-abrams-resolver now lives under the module name "ember/resolver"
Update to Ember 1.4.0 and Ember Data 1.0.0-beta.7
Merge pull request #507 from bradfol/update

Update to Ember 1.4.0 and Ember Data 1.0.0-beta.7
Fixed minor comment typo
Merge pull request #518 from existentialism/patch-1

Fixed minor comment typo
Merge pull request #502 from jgable/addImportValidate

Add module import validation
[fixes #521]
Rename _eak_seen to entries
Merge pull request #524 from teddyzeenny/entries

Rename _eak_seen to entries
[Fix #525] Make import validation optional
Merge pull request #528 from MajorBreakfast/master

[Fix #525] Make import validation optional