Fixed typo
Add option to manually refresh token

Sometimes the auto-refresh makes no sense if time between requests is very long.
For example if token lifetime is 10 mins and the requests are from hour to hour, some generated tokens will not be used at all.
Added auto option to refresh token when needed

Using the auto=true option the token will be auto-generated only when needed
Updated README to describe auto option
Refactor - Moved the auto refresh option in ctor

Second parameter to constructor now indicates if the token should be auto generated.
Remove auto parameter from other functions.
Updated README
Update README.md
Merge pull request #15 from sorinsarca/master

Add option to auto/manual refresh token