Posting a SPARQL command does not require urlencode
Allows the client to choose which POST type use in SPARQLUpdateStore
Reverse the postAsEncoded parameter in order to back-compatibility
Cleaned some duplicated lines and spurious comments
Cleaning up Dataset class, adding graph tracking to store API, as
discussed in #307

Summary of changes:

 * added methods ```add_graph``` and ```remove_graph``` to the Store
   API, implemented these for Sleepycat and IOMemory. A flag,
   ```graph_awareness``` is set on the store if they methods are
   supported, default implementations will raise an exception.

 * made the dataset require a store with the ```graph_awareness```
   flag set.

 * removed the graph-state kept in the ```Dataset``` class directly.

 * removed ```dataset.add_quads```, ```remove_quads``` methods. The
   ```add/remove``` methods of ```ConjunctiveGraph``` are smart enough
   to work with triples or quads.

 * removed the ```dataset.graphs``` method - it now does exactly the
   same as ```contexts```

 * cleaned up a bit more confusion of whether Graph instance or the
   Graph identifiers are passed to store methods. (#225)
added support for toggleable union of default graph
whitespace gardening
made dawg tests use dataset class
Dataset and graph_aware store fixes

Add graphs when parsing, so also empty graphs are added.
Optimization for IOMemory's __all_triples. fixes #318

Adding a __contextTriples index allows us to efficiently look-up
all triples in one context at linear cost of the store's size.
This is a common operation for example during serialization.

The previous implementation got along without this index, but
serializing a dataset with a lot of graphs took quadratic time.
Merge pull request #309 from RDFLib/graphaware

Dataset cleanup - Store API for graph method
make NodePickler picklable
added test for picklable NodePickler
Merge pull request #323 from gweis/master

make NodePickler picklable
fix PyPI link
Merge pull request #324 from ysangkok/patch-1

fix PyPI link
Added support for single-quoted Turtle string literals.
pyRdfa: superfluous warning was generated for an <a> element's @rel value, with a simple term and in RDFa Lite
Fixed duplicate creation of namespace prefixes
Only accept single quotes around strings when parsing Turtle, not N3.