Revert "esprima errors when upgrading PDF.js should not happen anymore."

Even in jshint 1.1.0 version they fixed all other package versions but
not esprima, which still links to master branch of GitHub repository and
confuses npm.

This reverts commit 64f42e4b868481bca35f3519233f5d46712792de.
Fix minor typo
Added comment describing the dummy text layer.
Merge pull request #207 from peerlibrary/new-annotations3

New annotations (in fact only highlights)