Update README.md

This is part of issue #31.

In this commit the `README.md` has been updated and expanded to
cover all the backend available.
Grammar changes

* Some fix from @abelsiqueira.
* Add link to article from Elizabeth D. Dolan and Jorge J. Moré in arXiv.
Fix REQUIREMENTS

* Remove the perprof line.
* Change `==` to `>=`.
Merge branch 'doc' into 'dev'
Upgrade version number to 0.1.0

This close #31.

TODO for 0.1.1:

[ ] Add some tests

TODO for 0.2.0:

[ ] Add PDF and SVG as matplotlib possibles outputs (more
    information about it in matplotlib documentation. (We will
    not enable PS and EPS output because this are old formats)
Add black and white option

This cover #33.

A flag `--black-and-white` was add and change color lines to styles
(dashed and dotted).
Merge pull request #34 from r-gaia-cs/bw

Black and white