added an 'aggregationLabel' attribute on colDef to be able to override the i18n translation

fixed test

fixed whitespaces

added an 'aggregationLabel' attribute on colDef to be able to override the i18n translation

fixed test

fixed whitespaces
Update pinning tutorial
Merge pull request #2282 from mathiasdose/issue2281

Update pinning tutorial
fix(Aggregation): Refactor introduced bug

Tests were failing and I did not notice. The function stopped returning
the actual values but was returning the aggregation text instead.
refactor(AutoResize): Avoid excessive $digests

Using $timeout for the loop to check whether the grid dimensions have
changed or not is causing a $digest() loop every 250ms. This can cause
quite a lot of slow-down in a large grid.

Changing to explicitly calling $apply() within a setTimeout() when the
dimensions have changed should fix this. The tests have been updated to
use Jasmine's async features to cover this alteration.

Fixes #2284. Fixes #2247
fix(Tests): Accidentally left in a ddescribe
Merge pull request #2237 from pedroclayman/master

added an 'aggregationLabel' attribute on colDef
Enh(headers): add sectionHeaders grid option for enabling section headers
Enh(headers): add getSectionWidth method for section header rendering
Enh(headers): add template for recursively rendering section headers