Improved performance of encodeHash by 30%.
 * Removed the use of two arrays to keep track of min/max lat/long
 * Removed the StringBuilder, and managed that ourselves.

Ran multiple iterations of 100000000 encodeHash(..), on a Intel i7
        Before changes average of 4,298,333 hases per second.
        After changes average of 5,625,000 hashes per second, with less object creations.
Merge branch 'speed' of github.com:bramp/geo
encodeHash: Removed the use of the BITS array.
New hashLengthToCoverBoundingBox() implementation (a hundred times faster).

Instead of fully calculating the hashes for each hash length
hashLengthToCoverBoundingBox now mimics the hash creation algorithm until
the point the results would differ.
Merge remote-tracking branch 'upstream/master'
Added two tests for hashLengthToCoverBoundingBox() to get full test coverage.
Merge remote-tracking branch 'upstream/master'
Merge pull request #13 from niqueco/master

Speed optimizations in encodeHash() and hashLengthToCoverBoundingBox()