Allow No Limit Parameter

[TruePath]

If one goes to the zotero api page and looks at the recommended means of syncing with the repository they suggest using format=versions to get the current versions of all objects. Unlike other requests a versions request (merely returning a dict mapping key -> version number) this request has no limit and the normal usage is to get all versions in one request. Indeed, it is important to be able to retrieve all version information in a single request so you know that your version information matches up with the last modified header.

Currently the add_parameters function always inserts a limit parameter. This can be hacked around by passing limit=-1 but this is undesirable and depends on unspecified behavior from the api. This change deletes the limit parameter if limit=None or limit=-1 is passed.

I also threw in a .gitignore ignoring the caches created by the test and a few deleted spaces at the end of lines.

[coveralls]

Coverage increased (+0.03%) to 40.952% when pulling a2845e3 on TruePath:allow_limit_to_be_unset into 3339b07 on urschrei:master.

[urschrei]

Thanks!