Remove all .pyc files on build.
Remove all .pyc files on build.

This fixes a bunch of ImportErrors when switching back and forth between the es and master branches. The git-ignored .pyc files are left alone, and Python happily loads them in various cases.
pelmers/dxr,KiemVM/Mozilla--dxr,bozzmob/dxr,jbradberry/dxr,jbradberry/dxr,jay-z007/dxr,kleintom/dxr,jbradberry/dxr,KiemVM/Mozilla--dxr,gartung/dxr,pombredanne/dxr,jay-z007/dxr,jay-z007/dxr,pombredanne/dxr,pelmers/dxr,jbradberry/dxr,jay-z007/dxr,nrc/dxr,KiemVM/Mozilla--dxr,nrc/dxr,kleintom/dxr,bozzmob/dxr,pombredanne/dxr,bozzmob/dxr,srenatus/dxr,gartung/dxr,nrc/dxr,srenatus/dxr,jay-z007/dxr,pelmers/dxr,nrc/dxr,kleintom/dxr,pombredanne/dxr,srenatus/dxr,nrc/dxr,KiemVM/Mozilla--dxr,gartung/dxr,srenatus/dxr,pombredanne/dxr,kleintom/dxr,pombredanne/dxr,gartung/dxr,kleintom/dxr,pelmers/dxr,jbradberry/dxr,gartung/dxr,srenatus/dxr,bozzmob/dxr,kleintom/dxr,pelmers/dxr,KiemVM/Mozilla--dxr,srenatus/dxr,pelmers/dxr,KiemVM/Mozilla--dxr,jbradberry/dxr,bozzmob/dxr,jay-z007/dxr,bozzmob/dxr,gartung/dxr,pelmers/dxr,jay-z007/dxr,kleintom/dxr,gartung/dxr,pombredanne/dxr,bozzmob/dxr,jbradberry/dxr,nrc/dxr