Update docs/usage/env.rst

Very minimal word correction
Fix typo in docstring
Adding support to shell_env on Windows. Fixes #804

Windows uses the sintax `SET name="value"` that is almost identical to the Linux counterpart.
Tested on Windows 7.
Fixing the test_use_of_path_appends_by_default
Add regression test re #581
Merge branch '1.5'
Read system known_hosts file.
Rewrite try/except block in cleaner style.
Updated changelog (for ssh_known_hosts handling).
Fix changelog re #730
Formatting
Don't email about Travis failures, only IRC
Merge branch '1.5'
Allow to override 'shell' argument passed to run/sudo in some contrib.files operations
Tweak language of main docstring, update versionadded, re #703
Attribution re #703
Convert to float in case 'wait' was passed in as a string.
Changelog re #791
Merge branch '1.5'

Conflicts:
	docs/changelog.rst
Fix for the 'SSH session not active' exception

Conflicts:
	fabric/state.py