notify: do not mime encode multipart templates
Mulitpart templates should take care of this themselves.
See http://www.selenic.com/pipermail/mercurial/2009-July/027017.html
Also catch potential parsing errors gracefully.
hg: config error at .../t/.hg/hgrc:1: 'invalid'
updating working directory
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
[paths]
default = .../foo%bar
default = .../foo%bar
bundle.mainreporoot=.../foobar
defaults.backout=-d "0 0"
defaults.commit=-d "0 0"
defaults.tag=-d "0 0"
paths.default=.../foo%bar
ui.slash=True