Update intersect.rst

Changes:
1) In couple of places the intersection line contains "chr" instead of "chr1". That is line: 135, 150, 173, 187․
2) When demonstrating -loj option, (line 172) the default intersection is used, however the result could be obtained by -wa -wb  mode. 
3) When demonstrating -u option, (line 260) the code runs default intersect, however the result shown, corresponds to that run with -wa option.