downloadprovider: Fail gracefully on Ubuntu 14.04 installs, add fallback
downloadprovider: Fail gracefully on Ubuntu 14.04 installs, add fallback

Provide a fallback so that installs with Python < 2.7.9 can still
receive updates. Some manual intervention is required, but now we can
provide working networking on any install that has either Python >=
2.7.9 or where a user can supply the requests[security] pip package

joshwatson/binaryninja-api,joshwatson/binaryninja-api,Vector35/binaryninja-api,Vector35/binaryninja-api,Vector35/binaryninja-api,Vector35/binaryninja-api,joshwatson/binaryninja-api,Vector35/binaryninja-api,joshwatson/binaryninja-api,Vector35/binaryninja-api,Vector35/binaryninja-api,joshwatson/binaryninja-api