utf-8 BOM support

hi MR. jcrocholl

I'm japanease developper. I can speak poor english. 
I fix pep8.py. error in reading utf-8 bom python script file.

sometime, utf-8 text file specify byte order mark(BOM) at the begginings of file.
http://en.wikipedia.org/wiki/Unicode

before fix. this is utf-8 text file with BOM.
```
#/usr/bin/env python
```

pep8  say this error. becourse "#!" is not start at beggings of file.
```
1:4: E261 at least two spaces before inline comment
```

at the reading lines,check 3 byte of beggings of file. if it is BOM, remove it.

and add testsuite/utf-8-bom.py for tests.

regard.