remove matplotlob source files
use pip to install matplotlib

a ploting library, (very old) version 0.91.1 is used

Conflicts:
	external/common/requirements.txt
update (prehistoric) matplotlib to a more recent version

was 0.91.1 recent stable is 1.2.1, chosen here is 1.1.1 -
new enough to build with gcc48 and numpy1.7, and old enough no API changes to code need to be applied.

fixes Mac support, gcc problems, improves graphics, see
http://matplotlib.org/users/whats_new.html

please test new functionality

Conflicts:
	external/common/requirements.txt
numpy is a dep for matplotlib

will conflict with other PR, resolve it

Conflicts:
	external/common/requirements.txt
remove pytz, provided in recent matplotlib

see https://bugs.archlinux.org/task/16327
hack for matplotlib's pip install problems

workaround for matplotlib and asteval install bug:
see http://stackoverflow.com/questions/11797688/matplotlib-requirements-with-pip-install-in-virtualenv
https://github.com/matplotlib/matplotlib/wiki/MEP11

numpy must be already installed, and requirements.txt file does not work, so do it manually
in build.sh before calling requirements.txt file

Conflicts:
	external/common/requirements.txt

Conflicts:
	build.sh