English corrections 'an host'

a for words starting with a for consonant sounds
an for words starting with a vowel sounds
Merge pull request #1337 from dgilm/patch-1

English corrections 'an host'
Fix Exception in arbiter when external module is providing objects. closes #1334
Fix: (reported by: flaf) bad behavior for use_aggressive_hot_checking.
Merge branch 'master' of https://github.com/naparuba/shinken
Fixed service totals and host totals

Hi!

The algorithm to get the % of OK services and OK hosts is wrong. There is a problem rounding the result. You will always lose precision with an amount of services greater than 100.

Here's an example:

```
>>> all_services = 9000
>>> problem_services = 20
>>> 100-problem_services*100/all_services
100
>>> # WTF! I have critical services and my status is still 100% OK? Mmmmm
...
>>> int(100-problem_services*100/float(all_services))
99
```

This avoid confusions at the currently dashboard (and maybe in other parts of shinken)
Merge pull request #1342 from dgilm/patch-2

Wrong % of services/hosts with status OK measure