Improve GetProviders Performance by around 2x

[kevina]

By doing a series of small improvements I was able to improve the query time in TestLargeProvidersSet by around 2x.

Improvement	Time (single CPU)	Speedup (from Initial)
Initial time	7290 ms	1x
Avoid go channels #38	6249 ms	1.2 x
Avoid redundant key check #38	3791 ms	1.92 x
Fast Base32 conversion (already in master)	3719 ms	1.96 x
Avoid unnecessary copy of databases Value ipfs/go-datastore#59	3430 ms	2.13 x

Does this belong in #38?

[kevina]

@lgierth all but the last part "Avoid unnecessary copy of databases Value" will be merged once #38 gets merged.

[kevina]

I also ran a bunch of other tests to determine other places of overhead, some highlights:

Test	Time
Without storing providers	2138 ms
Just Querying the Datastore (use datastore but no additional processing)	1480 ms
Directly Querying the LevelDB Database (no datastore layer)	912 ms

results.txt (for safe keeping).

[Stebalien]

@kevina do we still need this metaissue (maybe open separate issues for areas that still need to be improved).

[bigs]

closing for inactivity

[bitcard]

mark

[aschmahmann]

@bitcard I've seen you comment mark on a number of issues across recently. Any reason you're doing that over just subscribing to notifications from this issue? Adding one word comments adds a bunch of noise to GitHub notifications for everyone who is subscribed on the relevant issues or repos.