Use of ACME Directory and automatic update agreement to terms of service

* Update main script to:
  * Use the ACME directory to retrieve correct URLs from the ACME servers
  * Be able to update account informations (contact information and agreed terms of service)
  * Read terms of service links from either the ACME directory or account informations
  * Automatically update terms of service agreement with latest changes (user have to stay informed about the updates himself)
  * Fix HTTP errors handling
* Update configuration to:
  *  Configure ACME directory instead of CAUrl
  *  Allow to specify contact informations (email and phone number ; beware that Let's Encrypt servers don't allow phones)
* Update tests to:
  * Correctly setup before running tests without using global variable
  * Correctly clean setup after running tests (correctly remove ACME account and close temporary files)
  * Update requirements to latest dnspython release (as release 1.15 has fixed the dns updates issue)
* Update account delete script (you can find it in /tests/) according to updates of the main script

See merge request !5

Latest release of dnspython have fixed the bug from 1.14.0 release.

Note: as boulder doesn't currently support phone informations, we can't test it.

Clean log of useless headers
For base64, remove only trailing '=' as defined in acme drafts

As this variable is used with _send_signed_request we have
to be sure to not overwrite it in the script.

Set try count to begin with 1 and do 10 tries.

Enable ACMEDirectory for new-reg part.

Enable use of dynamic terms-of-service url for the agreement part too ( fixes #1 ).

Enable a way to add contact information inside account registration (email and phone).
It allows the ACME server provider to contact you on terms of service modifications.

Fix HTTPError exception handling (use correct error from urllib.error instead of IOError).

This part use ACMEDirectory in requests to ACME server.
Next part will remove last remaining CAUrl code and enable dynamic agreement url.

This commit update configuration constraints to use ACMEDirectory instead of CAUrl.
Next part will use effectively this new configuration to do requests to ACME server.

Clean tests and cover more code

Clean up tests code
Add some tests to cover more code

See merge request !4

logassert was added as requirements as the check have to look for log messages

DNS: fix search of dns host IP address configuration give us already an IP address



See merge request !3

tsig: simplifies algorithm list

The algorithm names match now the names used in dnssec-keygen and dnspython tools.

See merge request !2

The algorithm names match now the names used in dnssec-keygen and dnspython tools.

gitlab-ci: add master build badges to README



See merge request !1