Add touch_try_count and raise RequestException

[sebatyler]

Description

Update for my project using zappa is often failing. It is because of 2 reasons.

• Downloading dependency is facing read timeout. Message is below.

Downloading and installing dependencies..
 - ruamel.yaml==0.15.60: Downloading
HTTPSConnectionPool(host='files.pythonhosted.org', port=443): Read timed out. (read timeout=2)

• Checking touch_path is failing. Message is below.

Error: Warning! Status check on the deployed lambda failed. A GET request to '/' yielded a 504 response code.

Fatal error: local() encountered an error (return code 1) while executing 'zappa update prod'

So I want to add 'touch_try_count' setting and raise exception explicitly when request failed.

[coveralls]

Coverage decreased (-0.06%) to 72.947% when pulling c4b0677 on sebatyler:improve_update into 2019fe4 on Miserlou:master.

[sebatyler]

@jneves You approved this PR. Would it be merged? or not?