Faster hashing

1000000 Hashes
```
SM Timing
-----------
SizeT hash 	      1	00.061367	(00.061367 +- 00.000000)	[00.061367,00.061367]
String hash	      1	01.651815	(01.651815 +- 00.000000)	[01.651815,01.651815]
```
Ok, nvm. Basically I wanted to fix:
```
/home/titus/catkin_ws/src/Schweizer-Messer/sm_common/include/sm/hash_id.hpp:23:47: warning: large integer implicitly truncated to unsigned type [-Woverflow]
   static constexpr std::size_t kOffsetBasis = 14695981039346656037u;
```
Which I get on my VM, and can't wrap my head around it...