Added instructions to avoid MySQL Error 2002 

It is sometimes required to specifically mention the start of the mysql server to avoid the following error
```
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/tmp/mysql.sock' (2)
```
Updated error resources for ValueError for Mac OS X, Fixes #18
Merge pull request #17 from sudheesh001/master

Added instructions to avoid MySQL Error 2002
Simplified README
When importing and exporting files, also check for locale variants with underscore, e.g. de_AT, not just variants with dash
When updating files for download and commit: if project path not found, don't download/commit entire project instead, but do nothing instead and display error message.
We store entity strings and bytestrings to allow for case sensitive comparisons. Thus, we need to convert strings to unicode when needed. Only one problematic instance found so far. More details: https://docs.djangoproject.com/en/dev/ref/databases/#mysql-collation.
Encode amagama query as utf-8 and catch KeyError to prevent further server errors
If Gettext-based projects don't use Pontoon hooks (l10n comments in the DOM to define translatable nodes), match entities against DOM nodes with exact same contents
Change order of functions (from general to specific)
Also projects with .lang format might use hooks
If fuzzy translation approved without change, unfuzzy it
Non-priviliged users can unfuzzy existing translations