docs: fix misleading statement on "can't use jdk5 features" in README.md
docs: fix misleading statement on "can't use jdk5 features" in README.md

Java 1.5 features can be used since it is the minimal supported version for PgJDBC.

closes #294

jkutner/pgjdbc,jorsol/pgjdbc,lonnyj/pgjdbc,panchenko/pgjdbc,amozhenin/pgjdbc,pgjdbc/pgjdbc,amozhenin/pgjdbc,golovnin/pgjdbc,phillipross/pgjdbc,AlexElin/pgjdbc,sehrope/pgjdbc,AlexElin/pgjdbc,phillipross/pgjdbc,bocap/pgjdbc,pgjdbc/pgjdbc,jorsol/pgjdbc,lonnyj/pgjdbc,alexismeneses/pgjdbc,sehrope/pgjdbc,jamesthomp/pgjdbc,Gordiychuk/pgjdbc,jkutner/pgjdbc,AlexElin/pgjdbc,marschall/pgjdbc,davecramer/pgjdbc,whitingjr/pgjdbc,marschall/pgjdbc,rjmac/pgjdbc,zapov/pgjdbc,zemian/pgjdbc,rjmac/pgjdbc,zapov/pgjdbc,marschall/pgjdbc,underyx/pgjdbc,amozhenin/pgjdbc,panchenko/pgjdbc,underyx/pgjdbc,pgjdbc/pgjdbc,alexismeneses/pgjdbc,whitingjr/pgjdbc,jorsol/pgjdbc,marschall/pgjdbc,bocap/pgjdbc,whitingjr/pgjdbc,bocap/pgjdbc,lordnelson/pgjdbc,davecramer/pgjdbc,panchenko/pgjdbc,jorsol/pgjdbc,jamesthomp/pgjdbc,golovnin/pgjdbc,underyx/pgjdbc,golovnin/pgjdbc,lordnelson/pgjdbc,jkutner/pgjdbc,pgjdbc/pgjdbc,lordnelson/pgjdbc,schlosna/pgjdbc,zemian/pgjdbc,zapov/pgjdbc,davecramer/pgjdbc,sehrope/pgjdbc,rjmac/pgjdbc,Gordiychuk/pgjdbc,davecramer/pgjdbc,phillipross/pgjdbc,sehrope/pgjdbc,zemian/pgjdbc,jamesthomp/pgjdbc,Gordiychuk/pgjdbc,schlosna/pgjdbc