fix(select): do not override ng-model with empty selection on config change

closes #9
perf(options): use while loop instead of forEach to iterate over options
perf(options): use object as map instead of array and indexOf to lookup hashes
perf(ng-model): extract parsing ng-model expression from update function to do it once
perf(options): use object as map instead of array and indexOf to lookup options
chore(test): add charset meta tag
chore(test): increase number of options from 10 to 1000
chore(project): bump version to 0.4.6
docs(changelog): update changelog for 0.4.6
Merge branch 'hotfix/0.4.6'