Removing Python 2.5 from the Travis config since Jinja2 no longer supports it

The latest versions of Jinja2 no longer support Python 2.5 [[1], [2],
[3]]. Since Jinja2 is an integral part of Flask, this would also mean
that Flask no longer supports versions of Python prior to 2.6. Since
Flask no longer supports versions of Python prior to 2.6, plugins for
Flask do not need to support them either and so, the 2.5 Travis test
can be removed.

[1]: https://github.com/mitsuhiko/jinja2/pull/185#issuecomment-18098870
[2]: https://github.com/mitsuhiko/jinja2/commit/b89d1a8fe3fcbd73a8f4cebd4358eadebc2d8a9d
[3]: https://github.com/mitsuhiko/jinja2/commit/8bdc65d9e57d5c0da329bb88127d977bd58002e5
Fixed `__repr__` functions to work with Python 2.6 and above

In a Python 2.6 repl an exception is thrown when viewing instances of
the Filter, SearchParameters, and OrderyBy classes. This is because
the call to `str.format` in the `__repr__` method of each omits the
indexes for the arguments, which is a feature added in Python 2.7.

From the Python docs [7.1.3. Format String Syntax][1], "Changed in
version 2.7: The positional argument specifiers can be omitted, so '{}
{}' is equivalent to '{0} {1}'."

[1]: http://docs.python.org/2/library/string.html#format-string-syntax
Revert "Adds a wrapper around abort function to add JSON Content-Type."

This reverts commit 8aacd39d91777f10153424e47cbb5d1c2833491a.

Conflicts:
	tests/__init__.py
	tests/test_exceptions.py
Merge pull request #228 from goodscloud/remove-jsonhttpexception-dependency

Revert "Adds a wrapper around abort function to add JSON Content-Type."
Merge pull request #217 from croach/python2.6-fix

Updated `__repr__` methods for several classes to work with Python 2.6 and above
Merge pull request #215 from croach/remove-python25-from-travis-config

Removing Python 2.5 from Travis config since Jinja2 no longer supports it
Notes changes due to previous commits.
support SQL-standard date/datetime functions

This allows setting date and datetime type fields to the values `CURRENT_DATE`, `CURRENT_TIMESTAMP`, and `LOCALTIMESTAMP` from the API, and translates that into SQL expressions that get evaluated by the database.

This allows client-side code to set a date or timestamp to current as seen by the server, in case the client computer's clock is incorrect.
Groups third-party library imports together.
Places current time indicators in a module-level constant.
Documents changes due to previous commits.
Fixes issue 216.

Use query limit/offset on query instead of query result.
Merge pull request #225 from dnordberg/master-issue-216

Fixes issue 216: Paginated responses are extremely slow
Explicit declaration of exposed sub-resources.

Enables explicit declaration of exposed model sub-resources by
passing a `relationname` parameter to the `APIManager.create_api`
method.

This enables model relation endpoints to declare their own include and
exclude rules, methods, and post and pre processors.

If relationname is not passed to create_api, only the primary model
endpoints are created (e.g. /api/person, /api/person/1) you won't be
able to access other endpoints. Additional calls to create_api which
include the `relationname` parameter create the relation endpoints and
at this point include and exclude rules as well as post and pre
processors can be passed (Same as the primary model or different).

This also enables filtering of exposed relations using the same API.

This introduces two backwards incompatible changes.

1) Each exposed relation endpoint needs to be defined using `create_api`
   and passing the `relationname` parameter.

2) When passing `exclude_columns`, if you wish to exclude all relational data
   in a field, you only need to pass the field name, and not each field
   under the relation. For example,

   ```exclude_columns = ['country']```

   Instead of

   ```exclude_columns = ['country.name', 'country.code']```

This commit also updates the `has_field` doc string, which should also work
for `hybrid_property` fields.
Cleanup some logic to make it easier to follow.
Merge branch 'master-define-relation-endpoints' into master-patched

Conflicts:
	flask_restless/helpers.py