Added explanation on Hy <-> Python interop
Added @Tritlo to Authors
Tweak Python interop section a bit.
HyMacroExpansionError shouldn't truncate message

For example:

```
$ hy
hy 0.10.1 using CPython(default) 2.7.8 on Darwin
=> (defmacro hi [] (raise (TypeError "This message will be truncated")))
=> (hi)
  File "<input>", line 1, column 1

  (hi)
  ^--^
HyMacroExpansionError: `hi' message will be truncated
````
Add macro expansion in defclass
Fixes to language documentation

- Use backticks consistently for inline code
- Capitalize section headers and proper nouns
- Minor grammatical fixes
Fixes to contributor module documentation

- Changed "Contrib" to "Contributor"
- Fixed mismatched inline code in list* usage
- Added missing hyperlink targets
Change documentation code block language to Hy
Adhere to CPython's documentation guidelines

- Inline code is written using ``double backticks``
- Italicized text uses *asterisks* rather than `single backticks`
- Function parameters are italicized rather than written as inline code
Remove Python 3.2 from classifiers.
Fixes a long-standing bug in import under Python 3.3 and later.

Our MetaImporter was being inserted at the end of sys.meta_path.
For Python prior to 3.3, this was fine since sys.meta_path
was empty by default. As of the completion of PEP 302 in Py3.3 and
later, there are several importers registered by default. One of
these was trying (and failing) to import simple Hy modules,
resulting in a failure to import anything inside __init__.hy.

This change simply inserts the Hy-specific importer at the front
of the list.

This was noted in issue #620 (great catch @algernon)
Add clint as a dependency.

Since clint 0.3, it supports Python 3.
Miscellaneous changes to README

- Updated badges to utilize Shields
- Added alt-text to images
- Changed version/downloads badges to link to PyPI
- Use Markdown list to enumerate Hylarious Hacks
Fix error when 'let' context contains a non-symbol non-list
Remove branches configuration from .travis.yml.

"debian" branch has been already deleted.
Better error messages for fn/defn w/o arglists

When (fn) or (defn) does not get an arglist as first/second parameter,
emit a more descriptive error message, rather than an ugly traceback.

Fixes #716.

Reported-by: Joakim Tall
Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>