Fix parsing of default params and body params

- query_string_normalizer method is called multiple times from
  request.rb
- When it is called for default_params, we have to return the
  query_string in key=val format.
- When it is passed for body params which include a file, we need to
  send back the overridden way of [[key,val]] format.
- This difference makes sure that with default params, query string is
  generated properly and if the file params are present, body is
  generated properly.
Extract file_present? logic in a method
Install bundler first for travis to pass
Merge pull request #32 from prathamesh-sonpatki/params-normalization-issue

Params normalization issue
Bump version to 0.3.14
Check for instance of UploadIO

- This is required for objects which are not directly instances of File
  or Tempfile.
Added build status and gem version badge
 File presence check moved to a function
Merge pull request #33 from siddharthbhagwan/file_class_check

 File presence check moved to a function
Trying to make the TRANSFORMABLE_TYPES more generic
Added test for custom File like classes.
Updated README to include note about custom File classes.