drop references to Julia 0.3 in README, note that 0.4 or later works (closes #361)

Author: stevengj

README.md

@@ -19,7 +19,7 @@ without copying them.
 ## Installation
 
 Within Julia, just use the package manager to run `Pkg.add("PyCall")` to
-install the files.  Julia 0.4 is required.
+install the files.  Julia 0.4 or later is required.
 
 The latest development version of PyCall is available from
 <https://github.com/stevengj/PyCall.jl>.  If you want to switch to
@@ -159,8 +159,6 @@ Here are solutions to some common problems:
 * As mentioned above, use `foo[:bar]` and `foo[:bar](...)` rather than `foo.bar` and `foo.bar(...)`,
 respectively, to access attributes and methods of Python objects.
 
-* In Julia 0.3, sometimes calling a Python function fails because PyCall doesn't realize it is a callable object (since so many types of objects can be callable in Python).   The workaround is to use `pycall(foo, PyAny, args...)` instead of `foo(args...)`.   If you want to call `foo.bar(args...)` in Python, it is good to use `pycall(foo["bar"], PyAny, args...)`, where using `foo["bar"]` instead of `foo[:bar]` prevents any automatic conversion of the `bar` field.  In Julia 0.4, however, this problem goes away: all PyObjects are automatically callable, thanks to call overloading in Julia 0.4.
-
 * By default, PyCall [doesn't include the current directory in the Python search path](https://github.com/stevengj/PyCall.jl/issues/48).   If you want to do that (in order to load a Python module from the current directory), just run `unshift!(PyVector(pyimport("sys")["path"]), "")`.
 
 ## Python object interfaces
@@ -203,10 +201,9 @@ key, default)`.  Similarly, `set!(o, key, val)` is equivalent to
 o[key]` in Python.   For one or more *integer* indices, `o[i]` in Julia
 is equivalent to `o[i-1]` in Python.
 
-In Julia 0.4, you can call an `o::PyObject` via `o(args...)` just like
-in Python (assuming that the object is callable in Python).  In Julia
-0.3, you have to do `pycall(o, PyAny, args...)`, although the explicit
-`pycall` form is still useful in Julia 0.4 if you want to specify the
+You can call an `o::PyObject` via `o(args...)` just like in Python
+(assuming that the object is callable in Python).  The explicit
+`pycall` form is still useful in Julia if you want to specify the
 return type.
 
 #### Arrays and PyArray