Update NEWS.rst to 1.5.0.
updated yasnippet variable 'text' to 'yas-text'
Do not override company-backend for a call to dabbrev.

Overriding company-backend like this seems to have confuse company
at times, leading to the current backend being set to nil. Do not
let-bind the backend anymore, simply return the results of dabbrev
and tell company that we can have duplicates.

The latter reduces some performance, though.

Addresses #298.
Ensure that Rope won't re-check the whole project directory.

The previous hack did not take into account us calling validate(),
thereby throwing away our carefully-crafted file list. We now fully
replace the FileListCacher.

Addresses #309.
Bump version: 1.5.0 → 1.5.1