Added files from previous PR
Added separate method to Vector
Merge branch 'master' of https://github.com/sympy/sympy into newfunctions
Fixed travis errors
Changed lambdastr to dummy symbols if dummify=True

Previously, if the user declared alpha = symbols('\alpha'),
lambdastr would try to use \alpha as a variable. Now all
all symbols are replaced with dummies if dummify is true,
so any string is a valid variable name.

If the user wants to not use Dummy symbols, they can still
set dummify=False, and get direct substitution. This allows
the output to be examined, but will result in a syntax error
in lambdify if a non-valid symbol name is used (such as \alpha)
fix Dummy.sort_key and use it in expr.sort_key

Also, catch any new Numbers that are generated by the rebuilding
of terms in Mul.flatten. Rather than check them at each step of
the way, just handle them once when done traversing the args.
Give doctest section titles a line of whitespace beneath.
Merge branch 'master' of https://github.com/sympy/sympy into newfunctions
Added raises test to test_scalar_potential
Remove trailing whitespace.
Added taylor_term for sec(x)

Added taylor_term for sec(x).
Added unit tests corresponding to it.

Reference terms can be found here[1][2]

[1]https://www.efunda.com/math/taylor_series/trig.cfm
[2]https://en.wikipedia.org/wiki/Taylor_series

Updated variable usage, fixed formatting

Removed the declarations from the function call.
Added newline at the end.
Space after `,`

Added @cacheit. Fixed comments

Added @cacheit decorater.
Added space after `#` in comment.
Add early exit in the limit heuristics() for "bad" results with oo

    This does limit calculations in this method more
    fragle, which is good.  An example:
    >>> O(sin(1/x**2).contains(O(cos(1/x**2)))
    True
    was wrong, just because of this limit:
    >>> limit(sin(1/x**2)/cos(1/x**2), x, 0)
    sin(oo)/cos(oo)
Merge pull request #7300 from sushant-hiray/trig_taylor_term

Added taylor_term for sec(x)
Merge pull request #7297 from nebffa/issue_6588

Give doctest section titles a line of whitespace beneath.
Add Ben Lucato to the AUTHORS/aboutus. Welcome to SymPy!
Fix #7282 by replacing the shutdown_hook with the atexit module.
Add an extra config to sphinx to fix #6618.
Merge pull request #2922 from srjoglekar246/newfunctions

Basic field functions for sympy.physics.vector
DocFix: Replaced import mpmath with import sympy.mpmath
Merge pull request #7239 from smichr/dsort

fix Dummy.sort_key and use it in expr.sort_key