Remove mango_cursor_text.erl from path if dreyfus does not exist
Remove mango_cursor_text.erl from path if dreyfus does not exist

We create a new rebar.config.script for mango to rename
mango_cursor_text.erl so that compilation does not fail. If users
want to enable text search, they will manually have to clone
dreyfus and re-add the file (will be in README).

COUCHDB-2787

cloudant/couchdb-mango,kxepal/couchdb-mango,fkaempfer/couchdb,fkaempfer/couchdb,apache/couchdb-mango,fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb