Added default exponent to wait strategy

For ExponentialWait, the default exponent used is now set to 2.

Signed-off-by: Nate Brunette <n@tebru.net>
Added factories for each strategies

Signed-off-by: Nate Brunette <n@tebru.net>
Fixing method name typo

Signed-off-by: Nate Brunette <n@tebru.net>