Fix appveyor's cache

[ozkriff]

https://ci.appveyor.com/project/ozkriff/zemeroth/build/1.0.28/job/8cndcdxka0xpbprs#L104

Updating build cache...
Cache 'target' - Uploading (73,418,064 bytes)...100%Error uploading cache entry to the cache storage: The maximum cache size of 1,000 MB will be exceeded.
Cache 'C:\Users\appveyor\.cargo\registry' - Up to date
Build success

See https://www.appveyor.com/docs/build-cache/#cleaning-up-cache (?)

[ozkriff]

Disabled the cache for now: 15ad94e

[ozkriff]

Attempted to re-enable the cache in #125

[ozkriff]

Nnnope, still getting "The given key was not present in the dictionary." errors: https://ci.appveyor.com/project/ozkriff/zemeroth/build/1.0.199/job/ibjchxplb3f6x78m

:(

[ozkriff]

http://help.appveyor.com/discussions/problems/8572-cache-is-broken

[ozkriff]

\o/

Feodor Fitsner: Cache size is limited per account, not individual project, so probably cache is taken by other projects under your account?

Yay, deleting old projects caches fixed zemeroth's caching!