Fix LookupError for unknown encodings.

Sets the preferred encoding to UTF-8 if python is unable to find a codec
for the value returned by locale.getpreferedencodings() function.
Update contribManager list with recent contrib scripts
Merge PR #960
Update travis configuration to pull correct minecraft JAR

MC_VERSION will need to be adjusted as part of each update
More agressive texture cache

Especially with regard to jarfile loading
Merge PR #967