added check_strain()
added check_strain()

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