sed might be at /usr/bin/sed instead, stop depending on extended regex.

fixes #31
update to newer fast-export
pass --quiet to fast-export to make error cases more obvious, fixed #34
bump to latest fast-export
Merge remote-tracking branch 'offbytwo/master'

* offbytwo/master:
  pass --quiet to fast-export to make error cases more obvious, fixed #34
  update to newer fast-export
  sed might be at /usr/bin/sed instead, stop depending on extended regex.

Conflicts:
	Makefile
	bin/git-hg
change prefix to PREFIX in Readme to match Make convention
look for install and sed in path
fix prefix => PREFIX in Makefile too
use new repository for fast-export with fixes for hg 2.9
let the shell resolve sed rather instead of indirection through which. fixes #43
fixed git-hg-clone: hg-fast-export cannot find hgcheckout
improved hg.tracking format
update fast-import