corrects typo in add function description
groups sentences into paragraphs and adds subject to one sentence
Merge pull request #2351 from martco/master

Minor readability/grammatical updates to add function description
Provide the _blobSlice method only if the browser supports slicing Blobs.

Updated JSLint compatibility.
Added unit to head size comment.
Updated package version.
Merge branch 'master' into gh-pages