Manager-related functions refactoring
`getAvailableProviders` function
`postAccountName` function
Associated mock endpoints
Associated tests
Updated README.md
Merge branch 'master' into post-file-config-function
Merge branch 'master' into manager-endpoints
postFile: `config` function is asynchronous
Update associated tests
Update README.md with details about `postFile`
Fix README.md + English
`getAvailableProviders`: change arguments to an object
Merge pull request #50 from AnyFetch/post-file-config-function

`postFile` config function is asynchronous
Fix README.md
Merge pull request #49 from AnyFetch/manager-endpoints

Manager endpoints