extension for extract hyperlinks

[badbye]

Hi, this request tries to extract the hyperlinks in docx files.
Related issue: #9

I have to say that I did a lot of changes. However, it works as usual. I will really appreciate if you merge it.

Usage

I create a DOCReader class which store all the information of a docx file. After running the process method, the data attribute will store the text of header, footer, links, document.

obj = DOCReader(docx_file)
text = obj.process()
print obj.data['links']  # a list of tuple (text, hyperlink)

How it works

The hyperlinks are stored in the word/_rels/document.xml.rels file. All the links has a Id attribute, for example:

<Relationship Id="rId14" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/hyperlink" Target="https://www.google.com" TargetMode="External"/>

The corresponding texts are stored in the other documents, which also have the Id attributes.
When parsing the other documents (the xml2text method), I add some code to find the corresponding text.