Read.me: document default level value of info

Indicate that the default log level of a transport is info (not 'everything', as is currently implied).
Merge pull request #377 from erwinw/patch-2

Read.me: document default level value of info
[dist] Version bump. 0.7.3
Correct typo 'is' -> 'are'
Merge pull request #393 from fcolas6013/patch-1

Correct typo 'is' -> 'are'
Forgotten ) in String interpolation section.
Merge pull request #394 from ameesters/patch-1

Forgotten ) in String interpolation section.
Merge remote-tracking branch 'upstream/master'