Cookie support from Matej, with minor tweaks
When no arguments are passed, print usage.
Now code works on both Python 3 and Python 2
Fix unicode issues

Python 2 needs the unicode constructor in csv formatting.  Python 3 does
not have the unicode constructor anymore.  This commit adds a 'fake'
unicode constructor in Python 3 to ensure compatibility across python
versions.

Also, an encode function is provided, in Python 2, it calls encode('utf-8')
whereas, in Python 3, it directly returns the string.
Update to BeautifulSoup 4 + fix parser for bs4

In bs4, tag.get('class') is a list of classes. This commit fixes
the parser accordingly.
Support both BS4 and BeautifulSoup

BS4 and BeautifulSoup differ in the way the class attribute is defined.
In BS4, tag.class is a list of classes whereas in BeautifulSoup
tag.class is a string.

This commit abstract the class checker to support any of the two
versions.
Remove old svn keyword line.
Merge branch 'for-upstream' of https://github.com/pablooliveira/scholar.py into pablooliveira-for-upstream
Mergin pull request from Pablo Oliveira for Python 3 and BeautifulSoup 4
support (thanks!). Also a bunch of code cleanups and pylinting.
added PDF link option
added search by cluster id which was requested
updated README.md's example.
Substantial refactoring and feature additions.

This adds broad support for query arguments and retrieval of citation
data in exported formats such as BibTex, as well as minor changes such
as a logging framework and configuration and utility classes.

Version bump to 2.0.
Update README.md
Some typos fixed.
Additional features.

- Improved cookie support: the new --cookie-file options
  allows the reuse of a cookie across invocations of the tool;
  this allows higher query rates than would otherwise result
  when invoking scholar.py repeatedly.

- Workaround: remove the num= URL-encoded argument from parsed
  URLs. For some reason, Google Scholar decides to propagate
  the value from the original query into the URLs embedded in
  the results.
Update README.md

Added improved cookie support.
Added a logging option that reports full HTML contents, for debugging,
as well as incrementally more detailed logging via -d up to -dddd.
Merge branch 'master' of https://github.com/aliparsai/scholar.py into aliparsai-master

Conflicts:
	README.md
	scholar.py
Forgot to include PDF link extraction in one particular parser.