0.3.6

Fix range bug in index memory mapping #98
Add index memory mapping #97
Optimize SPIFFS_read for large files #96
Add temporal cache for opening files #95
More robust gc #93 (thanks @dismirlian)
Fixed a double write of same data in certain cache situations
Fixed an open bug in READ_ONLY builds
File not visible in SPIFFS_readdir #90 (thanks @benpicco-tmp)
Cache load code cleanup #92 (thanks @niclash)
Fixed lock/unlock asymmetry #88 #87 (thanks @JackJefferson, @dpruessner)
Testframe updates
New API functions:

SPIFFS_ix_map - map index meta data to memory for a file
SPIFFS_ix_unmap - unmaps index meta data for a file
SPIFFS_ix_remap - changes file offset for index metadata map
SPIFFS_bytes_to_ix_map_entries - utility, get length of needed vector for given amount of bytes
SPIFFS_ix_map_entries_to_bytes - utility, get number of bytes a vector can represent given length
New config defines:

SPIFFS_IX_MAP - enable possibility to map index meta data to memory for reading faster
SPIFFS_TEMPORAL_FD_CACHE - enable temporal cache for opening files faster
SPIFFS_TEMPORAL_CACHE_HIT_SCORE - for tuning the temporal cache