Minor wording changes and a couple spelling fixes
Merge pull request #1271 from carsonmcdonald/mrbgemdocfixes

Minor wording changes and a couple spelling fixes
Describe GemBox files can be located anywhere
No need to specify empty bin list anymore(example)
do not specify implementation dependant exception class names in fiber test
install gperf to prevent accidental compile error
Merge branch 'master' of github.com:mruby/mruby
Merge pull request #1272 from kyab/absolute_path_ok_for_gembox

Describe GemBox files can be located anywhere
Merge pull request #1273 from kyab/no_bins_example

No need to specify empty bin list anymore(example)