Remove PYTHONOPTIMIZE=2 workarounds from install.sh

[yajo]

install.sh includes some workarounds for pip-installing some packages that don't support PYTHONOPTIMIZE=2 at install time or fail somehow.

"Fixing" those workarounds means removing them when Odoo depends on a version of the package that has these bugs fixed:

• http://stackoverflow.com/questions/41913122/error-requirements-pyparsing-1-5-7-odoo-8
  • Odoo 8 requires 1.5.7, but it does not use it. Workaround: install same version as in Odoo 9.
  • Odoo 9 and 10 use an installable version.
• Cannot install psutil with PYTHONOPTIMIZE=2 giampaolo/psutil#948, fixed on psutil>=5.1.0
  • Odoo 8 uses 2.1.1; cannot fix.
  • Odoo 9 uses 2.2.0; cannot fix.
  • Odoo 10 uses 4.3.1; cannot fix.
• Cannot install with PYTHONOPTIMIZE=2 pydot/pydot#145, fix on master.
  • Odoo 8 uses 1.0.2
  • Odoo 9 uses 1.0.2
  • Odoo 10 uses 1.2.3
• psycopg/psycopg2@37d80f2, fixed on psycopg2>=2.6.
  • Odoo 8 uses 2.5.3; cannot fix.
  • Odoo 9 uses 2.5.4; cannot fix.
  • Odoo 10 uses 2.6.2; fixed.
• Fix use of __doc__ in setup.py for -OO mode skarim/vobject#19, fixed on vobject>=0.9.3.
  • Odoo 8 uses 0.6.6; cannot fix.
  • Odoo 9 uses 0.6.6; cannot fix.
  • Odoo 10 uses 0.9.3; fixed.