Try to use F# 3.1 for Travis build - fixing #459
Revert "Try to use F# 3.1 for Travis build - fixing #459"

This reverts commit 28f094d485ecd0908bd62b88941061b24233bddb.
Fix issue where new CLI treated target=Clean as the positional target name.  Now reject positional argument containing =.  FAKE build.cmd example works and falls back to old CLI as expected.
Merge remote-tracking branch 'upstream/master' into new-cli
Merge pull request #465 from bentayloruk/new-cli

Fix for build.cmd failure issue on new CLI