v4.5.0

Big feature: Integrate with https://github.com/github/linguist for filetype detection. Also:

0df1bfa Add requirements.txt support, closes #507
f7302d9 Add jq syntax, closes #502
7e38f42 Add improved sql syntax, closes #505
e521ba3 Add fennel support, closes #514
ee4f515 Add ftdetect for jsonnet
20a388c Add jsonnet support, closes #515
5670985 Add docs, fixes #501
f8cee01 Allow to set let g:python_highlight_all = 0, closes #474
c6936ae Fix dhall plugin, closes #519
a3bdbcd Fix svelte branch name, closes #522
9c3c0bc Fix rspect ftdetect, #503
8b6c06e Add detection for rspec files (#503)