Now supports direct binary output.
Merge pull request #6 from wiegand/feature-binary-support

Now supports direct binary output.

Pull request description:

pandoc supports several binary output formats (i.e. odt, docx, epub, and 
epub3), however pandoc requires these to output to files instead of dumping
the binary to standard output. From the README:

> Output goes to stdout by default (though output to stdout is disabled for
> the odt, docx, epub, and epub3 output formats).

This pull request eliminates this restriction by outputting the binary
directly to standard output for odt, docx, epub, and epub3 output formats.
(It also adds the missing epub3 output format.)

Benefits:

* binary support!
* the API now works consistently across all output formats
* much easier in cases where you want to dynamically serve some exported data
  in a variety of formats to a users of your web application, i.e. no more
  fiddling with files
Updating Readme format information.
Updating development and test bundler gems.
Version bump to 0.7.0
Removing Jeweler dependency.

Jeweler is locked to older versions of Ruby and is largely unnecessary,
so removing in favor of just using the gem command.

In the process, adding rake to the Gemfile and using string array
shortcut for file list in gemspec.
Version bump to 0.7.1
Simplifying option stringification.

The `#convert_options` method was convoluted, so replacing with a
slightly clearer series of option stringification methods.
Refactoring binary conversion.

Avoiding traversing the option list twice to determine whether to output
binary. Also making it clearer that there is string and binary output by
creating a method for each one.

The output file option is set explicitly here, which is hacky but retains
the existing temp file behavior. However, this could cause problems if a
user specifies their own output option, so this will need to be updated.
Updating PandocRuby::WRITERS to include binary writers.
Renaming #stringify_options to #prepare_options

Since the method does more than simply convert them to strings, this
method name is more accurate.
Adding documentation and removing explicit self from private method calls.
Minor Readme tweak.
Version bump to 0.7.2
Renaming #option_flag to #format_flag

This method returns a formatted string version of the flag and its optional
argument and does nothing else, so changing the name to reflect this.
Moving temp file assignment out of begin ... end
Removing redundant nil check
Version bump to 0.7.3
Fixing typo: options_string -> option_string
Version bump to 0.7.4