Add ssl_certs_file arg and config for custom ca bundles

tests/samples/configs/has_everything.cfg

@@ -13,6 +13,7 @@ include_only_with_project_file = false
 offline = false
 proxy = https://user:pass@localhost:8080
 no_ssl_verify = false
+ssl_certs_file =
 timeout = abc
 api_url = https://localhost:0/api/v1/heartbeats
 hostname = fromcfgfile

tests/samples/configs/ssl_custom_certfile.cfg

@@ -0,0 +1,18 @@
+[settings]
+verbose = true
+api_key = d491a956-c8f2-44a9-98a7-987814bd71ba
+log_file = /tmp/waka
+hide_filenames = true
+exclude =
+    ^COMMIT_EDITMSG$
+    ^TAG_EDITMSG$
+    ^/var/
+    ^/etc/
+include =
+    .*
+offline = false
+proxy = https://user:pass@localhost:8080
+ssl_certs_file = /fake/ca/certs/bundle.pem
+timeout = abc
+api_url = https://localhost:0/api/v1/heartbeats
+hostname = fromcfgfile

tests/samples/configs/ssl_verify_disabled.cfg

@@ -13,6 +13,7 @@ include =
 offline = false
 proxy = https://user:pass@localhost:8080
 no_ssl_verify = true
+ssl_certs_file =
 timeout = abc
 api_url = https://localhost:0/api/v1/heartbeats
 hostname = fromcfgfile

tests/samples/output/common_usage_header

@@ -1,7 +1,8 @@
 usage: wakatime [-h] [--entity FILE] [--key KEY] [--write] [--plugin PLUGIN]
                 [--time time] [--lineno LINENO] [--cursorpos CURSORPOS]
                 [--entity-type ENTITY_TYPE] [--category CATEGORY]
-                [--proxy PROXY] [--no-ssl-verify] [--project PROJECT]
+                [--proxy PROXY] [--no-ssl-verify]
+                [--ssl-certs-file SSL_CERTS_FILE] [--project PROJECT]
                 [--alternate-project ALTERNATE_PROJECT] [--language LANGUAGE]
                 [--local-file FILE] [--hostname HOSTNAME] [--disable-offline]
                 [--hide-file-names] [--hide-project-names] [--exclude EXCLUDE]

tests/samples/output/test_help_contents

@@ -29,6 +29,9 @@ optional arguments:
                         socks5://user:pass@host:port or domain\user:pass
   --no-ssl-verify       Disables SSL certificate verification for HTTPS
                         requests. By default, SSL certificates are verified.
+  --ssl-certs-file SSL_CERTS_FILE
+                        Override the bundled Python Requests CA certs file. By
+                        default, uses certifi for ca certs.
   --project PROJECT     Optional project name.
   --alternate-project ALTERNATE_PROJECT
                         Optional alternate project name. Auto-discovered