update docs (small fixes in doc/installation.rst)
update docs (small fixes in doc/installation.rst)

vlukes/sfepy,BubuLK/sfepy,vlukes/sfepy,sfepy/sfepy,rc/sfepy,BubuLK/sfepy,RexFuzzle/sfepy,rc/sfepy,lokik/sfepy,vlukes/sfepy,lokik/sfepy,BubuLK/sfepy,lokik/sfepy,RexFuzzle/sfepy,sfepy/sfepy,RexFuzzle/sfepy,sfepy/sfepy,rc/sfepy,lokik/sfepy,RexFuzzle/sfepy