Fix property name for entry object

It appears from a raw log of entry object that the property name is 'gs:cell'
Fix usage of saved reference to 'this'
Check dynamically response format from WS calls

Google Spreadsheet services may return an empty object if when asked for JSON format (alt=json in url)
Try to parse JSON output in request method, and then try to parse it as XML if the JSON attempt failed
Should solve #29
Merge pull request #33 from Pingflow/pr-response-format

Pr response format
Fixes worksheetTitle and worksheetUpdated being null

When receiving Worksheet info, worksheetTitle was null and
worksheetUpdated was an invalid date. result.feed.title.$t and
result.feed.updated.$t does not exist which causes the issue.
If sheet is unreadable, trigger error (rather than crash)
Merge pull request #37 from ejb/patch-1

If sheet is unreadable, trigger error (rather than crash)
bump
Merge pull request #36 from jleplomet/stable

Fixes worksheetTitle and worksheetUpdated being null
0.2.9
Fix #38

Considers result from request an object and get error information from it.
allow non adds to send
yellow
allow batchupdate
fix
some comments
Merge pull request #1 from gebrits/stable
Update return value for cell

cell.$t encodes HTML text if used in spreadsheet. cell.inputValue
return text as written.
Merge pull request #39 from ssimono/stable

Closes #38
0.2.10